RULES defined from TemplateHaskell get rejected by ghc

To repro in HEAD:

ghci> {-# RULES "" forall a b c. a * c + b * c = (a + b) * c #-} -- ok

ghci> :{
ghci| f x = x
ghci| $( [d| {-# RULES "" forall a b c. a * c + b * c = (a + b) * c #-} |] ) -- fail
ghci| :}

<interactive>:13:2: error:
    Rule "":
      Illegal expression: ((a_a2ft * c_a2fv) + (b_a2fu * c_a2fv))
      in left-hand side: ((a_a2ft * c_a2fv) + (b_a2fu * c_a2fv))
    LHS must be of form (f e1 .. en) where f is not forall'd

This is due to extra parens may be added by TemplateHaskell, this used to be even worse that followings would be rejected as well:

$( [d| {-# RULES "." forall a b. (.) a b foo = a (b foo) #-} |] )
$( [d| {-# RULES "foo" forall a b. foo a b = a b #-} |] )

but have been mitigated by 30e625e6

We may just be more flexible when validating the LHS as we compile to the same CoreExpr after removing the parens.