This rename was made as part of
https://github.com/llvm/llvm-project/pull/147835 in order to ease
rebasing the PR, and give a nice window for other patches to get rebased
as well.

It has been a while already, so lets go ahead and rename it back.

This fixes the transform to use the correct parameter type for an
AssociatedDecl which has been fully specialized.

Instead of using the type for the parameter of the specialized template,
this uses the type of the argument it has been specialized with.

This fixes a regression reported here:
https://github.com/llvm/llvm-project/pull/161029#issuecomment-3375478990

Since this regression was never released, there are no release notes.

A DependentTemplateSpecializationType (DTST) is basically just a
TemplateSpecializationType (TST) with a hardcoded DependentTemplateName
(DTN) as its TemplateName.

This removes the DTST and replaces all uses of it with a TST, removing a
lot of duplication in the implementation.

Technically the hardcoded DTN is an optimization for a most common case,
but the TST implementation is in better shape overall and with other
optimizations, so this patch ends up being an overall performance
positive:
<img width="1465" height="38" alt="image"
src="https://github.com/user-attachments/assets/084b0694-2839-427a-b664-eff400f780b5"
/>

A DTST also didn't allow a template name representing a DTN that was
substituted, such as from an alias template, while the TST does allow it
by the simple fact it can hold an arbitrary TemplateName, so this patch
also increases the amount of sugar retained, while still being faster
overall.

Example (from included test case):
```C++
template<template<class> class TT> using T1 = TT<int>;
template<class T> using T2 = T1<T::template X>;
```

Here we can now represent in the AST that `TT` was substituted for the
dependent template name `T::template X`.

Adds support for unbounded resource arrays declared at a global scope. Local unbounded resource array variables or incomplete resource arrays as function arguments are not going be supported in HLSL in Clang. See:
 - https://github.com/microsoft/hlsl-specs/issues/141
 - https://github.com/llvm/wg-hlsl/pull/298

Closes #145427

This is a small performance improvement:

This helps recover the performance lost in #155028, reversing it into a
small positive instead.
<img width="1464" height="20" alt="image"
src="https://github.com/user-attachments/assets/3378789e-109d-4211-846e-0d38d6cb190a"
/>

This reintroduces `Type.h`, having earlier been renamed to `TypeBase.h`,
as a redirection to `TypeBase.h`, and redirects most users to include
the former instead.

This is a preparatory patch for being able to provide inline definitions
for `Type` methods which would otherwise cause a circular dependency
with `Decl{,CXX}.h`.

Doing these operations into their own NFC patch helps the git rename
detection logic work, preserving the history.

This patch makes clang just a little slower to build (~0.17%), just
because it makes more code indirectly include `DeclCXX.h`.

This is a preparatory patch, to be able to provide inline definitions
for `Type` functions which depend on `Decl{,CXX}.h`. As the latter also
depends on `Type.h`, this would not be possible without some
reorganizing.

Splitting this rename into its own patch allows git to track this as a
rename, and preserve all git history, and not force any code
reformatting.

A later NFC patch will reintroduce `Type.h` as redirection to
`TypeBase.h`, rewriting most places back to directly including `Type.h`
instead of `TypeBase.h`, leaving only a handful of places where this is
necessary.

Then yet a later patch will exploit this by making more stuff inline.

A number of builtins report some variation of "this type is compatibile
with some bitwise equivalent operation", but this is not true for
address discriminated values. We had address a number of cases, but not
all of them. This PR corrects the remaining builtins.

Fixes #154394

And make use of those.

These changes are split from prior PR #155028, in order to decrease the
size of that PR and facilitate review.