Revert "Following up on PR48517, fix handling of template arguments that refer"

Combined with 'da986511 - Revert "DR2064:
decltype(E) is only a dependent', this change (5a391d38) caused verifier
errors when building Chromium. See https://crbug.com/1168494#c1 for a
reproducer.

Additionally it reverts changes that were dependent on this one, see
below.

> Following up on PR48517, fix handling of template arguments that refer
> to dependent declarations.
>
> Treat an id-expression that names a local variable in a templated
> function as being instantiation-dependent.
>
> This addresses a language defect whereby a reference to a dependent
> declaration can be formed without any construct being value-dependent.
> Fixing that through value-dependence turns out to be problematic, so
> instead this patch takes the approach (proposed on the core reflector)
> of allowing the use of pointers or references to (but not values of)
> dependent declarations inside value-dependent expressions, and instead
> treating template arguments as dependent if they evaluate to a constant
> involving such dependent declarations.
>
> This ends up affecting a bunch of OpenMP tests, due to OpenMP
> imprecisely handling instantiation-dependent constructs, bailing out
> early instead of processing dependent constructs to the extent possible
> when handling the template.
>
> Previously committed as 8c1f2d15, and
> reverted because a dependency commit was reverted.

This reverts commit 5a391d38.

It also restores clang/test/SemaCXX/coroutines.cpp to its state before
da986511.

Revert "[c++20] P1907R1: Support for generalized non-type template arguments of scalar type."

> Previously committed as 9e08e51a, and
> reverted because a dependency commit was reverted. This incorporates the
> following follow-on commits that were also reverted:
>
> 7e84aa1b by Simon Pilgrim
> ed13d8c6 by me
> 95c7b6ca by Sam McCall
> 430d5d84 by Dave Zarzycki

This reverts commit 4b574008.

Revert "[msabi] Mangle a template argument referring to array-to-pointer decay"

> [msabi] Mangle a template argument referring to array-to-pointer decay
> applied to an array the same as the array itself.
>
> This follows MS ABI, and corrects a regression from the implementation
> of generalized non-type template parameters, where we "forgot" how to
> mangle this case.

This reverts commit 18e093fa.