[BoundsSafety] Delay processing of bounds attrs in templates

[delcypher]

This is a cherry-pick of change that was landed to stable/20240723 (#9929) but not landed on the next branch.

Aside from resolving merge conflicts it was also necessary to modify the clang/test/BoundsSafety/(AST|Sema)/value-dependence.cpp tests because they fail to work when the new bounds checks are enabled (rdar://150044760). To workaround that the test has been made to disable the new return_size bounds check when -fbounds-safety is enabled with C++.

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• [BoundsSafety] Delay processing of bounds attrs in templates

Dynamic bounds attributes do not handle value dependent arguments. To enable wider interop with C++ code bases we delay the processing of these attributes inside templated contexts. Instead we apply the new type while instantiating the function.

One issue with this approach is that instantiation happens after parsing is finished, and the Scope information we use to prevent attributes from referring to arguments from outer scopes is only available during parsing. These diagnostics were emitted at the end of the type processing. In templated contexts we instead perform that analysis during parsing, and delay the rest of the processing. To avoid churn in unrelated tests the rest of the attributes keep their processing as is, until we've investigated what impact hoisting it would have on the user experience.

Conflicts:
clang/include/clang/Sema/Sema.h
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/SemaCXX/warn-unsafe-buffer-usage-count-attributed-pointer-argument.cpp

rdar://150694971

(cherry picked from commit c87bc75)

[delcypher]

@swift-ci test llvm

[delcypher]

@swift-ci test