This cleanup patch: refactors a bunch of duplicates of
* Refactors a bunch of duplicates of getDecltypeForParenthesizedExpr into
a common implementation.
* Converts `Expr->getValueKind()` uses into calls to `is?Value` helpersgetDecltypeForParenthesizedExpr into a common implementation.
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>