template-haskell: Move wired-ins to ghc-internal

Thus we make `template-haskell` reinstallable and keep it as the public
API for Template Haskell.
All of the wired-in identifiers are moved to `ghc-internal`.
This necessitates also moving much of `ghc-boot-th` into `ghc-internal`.
These modules are then re-exported from `ghc-boot-th` and
`template-haskell`.
To avoid a dependency on `template-haskell` from `lib:ghc`, we instead
depend on the TH ASTs via `ghc-boot-th`.

As `template-haskell` no longer has special status, we can drop the
logic adding an implicit dependency on `template-haskell` when using TH.
We can also drop the `template-haskell-next` package, which was
previously used when bootstrapping.

When bootstrapping, we need to vendor the TH AST modules from
`ghc-internal` into `ghc-boot-th`. This is controlled by the `bootstrap`
cabal flag as before. See Note [Bootstrapping Template Haskell].

We split out a GHC.Internal.TH.Lift module resolving #24752.
This module is only built when not bootstrapping.

Resolves #24703

-------------------------
Metric Increase:
    ghc_boot_th_dir
    ghc_boot_th_so
-------------------------