Make known names simple ConApps (#19386)

While fixing #17336 we noticed that code like this:

 = if | tc == intTyConName     -> ...
      | tc == int8TyConName    -> ...
      | tc == int16TyConName   -> ...
      | tc == int32TyConName   -> ...
      | tc == int64TyConName   -> ...
      | tc == wordTyConName    -> ...
      | tc == word8TyConName   -> ...
      | tc == word16TyConName  -> ...
      | tc == word32TyConName  -> ...
      | tc == word64TyConName  -> ...
      | tc == naturalTyConName -> ...

was not transformed into a single case expression on the Name's unique
as I would have expected but as a linear search. Bindings for known
names are not simple constructor applications because of their strict
`n_occ :: !OccName` field that needs to allocate a `FastString`: this
field needs to be forced before using the `n_unique` field.

This patch partially reverses ccaf7b66 by
making `n_occ` lazy and by ensuring that helper functions used to
declare known names are fully inlined. The code above is then
optimised as expected.

                                         Baseline
                     Test    Metric         value     New value Change
---------------------------------------------------------------------------
 ManyAlternatives(normal) ghc/alloc   822810880.0   822104032.0  -0.1%
 ManyConstructors(normal) ghc/alloc  4551734924.0  4480621808.0  -1.6%
MultiLayerModules(normal) ghc/alloc  6029108292.0  6016024464.0  -0.2%
         Naperian(optasm) ghc/alloc    57396600.0    56826184.0  -1.0%
        PmSeriesG(normal) ghc/alloc    55666656.0    54521840.0  -2.1%
        PmSeriesS(normal) ghc/alloc    70204344.0    69047328.0  -1.6%
        PmSeriesT(normal) ghc/alloc   102273172.0   101070016.0  -1.2%
        PmSeriesV(normal) ghc/alloc    69157156.0    68002176.0  -1.7%
           T10421(normal) ghc/alloc   129875476.0   128881544.0  -0.8%
          T10421a(normal) ghc/alloc    92031552.0    90982800.0  -1.1%
           T10547(normal) ghc/alloc    34399800.0    33016760.0  -4.0% GOOD
           T10858(normal) ghc/alloc   208316964.0   207318616.0  -0.5%
           T11195(normal) ghc/alloc   304100548.0   302797040.0  -0.4%
           T11276(normal) ghc/alloc   140586764.0   139469832.0  -0.8%
          T11303b(normal) ghc/alloc    52118960.0    51120248.0  -1.9%
           T11374(normal) ghc/alloc   241325868.0   240692752.0  -0.3%
           T11822(normal) ghc/alloc   150612036.0   149582736.0  -0.7%
           T12150(optasm) ghc/alloc    92738452.0    91897224.0  -0.9%
           T12227(normal) ghc/alloc   494236296.0   493086728.0  -0.2%
           T12234(optasm) ghc/alloc    66786816.0    65966096.0  -1.2%
           T12425(optasm) ghc/alloc   112396704.0   111471016.0  -0.8%
           T12545(normal) ghc/alloc  1832733768.0  1828021072.0  -0.3%
           T12707(normal) ghc/alloc  1054991144.0  1053359696.0  -0.2%
           T13035(normal) ghc/alloc   116173180.0   115112072.0  -0.9%
           T13056(optasm) ghc/alloc   391749192.0   390687864.0  -0.3%
           T13253(normal) ghc/alloc   382785700.0   381550592.0  -0.3%
       T13253-spj(normal) ghc/alloc   168806064.0   167987192.0  -0.5%
           T13379(normal) ghc/alloc   403890296.0   402447920.0  -0.4%
           T13701(normal) ghc/alloc  2542828108.0  2534392736.0  -0.3%
           T13719(normal) ghc/alloc  4666717708.0  4659489416.0  -0.2%
             T14052(ghci) ghc/alloc  2181268580.0  2175320640.0  -0.3%
           T14683(normal) ghc/alloc  3094166824.0  3094524216.0  +0.0%
           T14697(normal) ghc/alloc   376323432.0   374024184.0  -0.6%
           T15164(normal) ghc/alloc  1896324828.0  1893236528.0  -0.2%
           T15630(normal) ghc/alloc   198932800.0   197783656.0  -0.6%
           T16190(normal) ghc/alloc   288186840.0   287250024.0  -0.3%
           T16577(normal) ghc/alloc  8324100940.0  8321580600.0  -0.0%
           T17096(normal) ghc/alloc   318264420.0   316961792.0  -0.4%
           T17516(normal) ghc/alloc  1332680768.0  1331635504.0  -0.1%
           T17836(normal) ghc/alloc  1296308168.0  1291098504.0  -0.4%
          T17836b(normal) ghc/alloc    62008340.0    60745256.0  -2.0%
           T17977(normal) ghc/alloc    52954564.0    51890248.0  -2.0%
          T17977b(normal) ghc/alloc    47824016.0    46683936.0  -2.4%
           T18140(normal) ghc/alloc   117408932.0   116353672.0  -0.9%
           T18223(normal) ghc/alloc  5603767896.0  5602037104.0  -0.0%
           T18282(normal) ghc/alloc   166456808.0   165396320.0  -0.6%
           T18304(normal) ghc/alloc   103694052.0   103513136.0  -0.2%
           T18478(normal) ghc/alloc   816819336.0   814459560.0  -0.3%
          T18698a(normal) ghc/alloc   438652404.0   437041784.0  -0.4%
          T18698b(normal) ghc/alloc   529448324.0   527666608.0  -0.3%
           T18923(normal) ghc/alloc    78360824.0    77315560.0  -1.3%
            T1969(normal) ghc/alloc   854223208.0   851303488.0  -0.3%
            T3064(normal) ghc/alloc   200655808.0   199368872.0  -0.6%
            T3294(normal) ghc/alloc  1791121792.0  1790033888.0  -0.1%
            T4801(normal) ghc/alloc   343749816.0   341760680.0  -0.6%
            T5030(normal) ghc/alloc   377520872.0   376492360.0  -0.3%
          T5321FD(normal) ghc/alloc   312680408.0   311618536.0  -0.3%
         T5321Fun(normal) ghc/alloc   355635656.0   354536264.0  -0.3%
            T5631(normal) ghc/alloc   629667068.0   629562192.0  -0.0%
            T5642(normal) ghc/alloc   540913864.0   539569952.0  -0.2%
            T5837(normal) ghc/alloc    43183652.0    42177928.0  -2.3%
            T6048(optasm) ghc/alloc    96395616.0    95397032.0  -1.0%
             T783(normal) ghc/alloc   427778908.0   426307760.0  -0.3%
            T9020(optasm) ghc/alloc   279523960.0   277010040.0  -0.9%
            T9233(normal) ghc/alloc   966717488.0   964594096.0  -0.2%
            T9630(normal) ghc/alloc  1585228636.0  1581428672.0  -0.2%
            T9675(optasm) ghc/alloc   594817892.0   591703040.0  -0.5%
           T9872a(normal) ghc/alloc  2216955420.0  2215648024.0  -0.1%
           T9872b(normal) ghc/alloc  2747814924.0  2746515472.0  -0.0%
           T9872c(normal) ghc/alloc  2271878772.0  2270554344.0  -0.1%
           T9872d(normal) ghc/alloc   623661168.0   621434064.0  -0.4%
            T9961(normal) ghc/alloc   409059124.0   406811120.0  -0.5%
            WWRec(normal) ghc/alloc   940563924.0   938008112.0  -0.3%
           hie002(normal) ghc/alloc  9801941116.0  9787675736.0  -0.1%
       parsing001(normal) ghc/alloc   494756632.0   493828512.0  -0.2%

Metric Decrease:
    T10547
    T13035
    T12425