ASan: Remove noexcept from __sanitizer_annotate_contiguous_container

[StephanTLavavej]

#4106 marked __sanitizer_annotate_contiguous_container as noexcept because it's extern "C". However, it has to match ASan's primary declaration, so we can't mark it.

This PR reverts this declaration to its original form, and adds a comment for future maintainers.

[AlexGuteniev]

If it throws, should be noexcept(false) to opt out of implicit noexcept, no?

[CaseyCarter]

If it throws, should be noexcept(false) to opt out of implicit noexcept, no?

I don't believe it does throw, I think it's simply unannotated. This is common for shared C/C++ headers: it's easy to stick a conditional extern "C" { ... } around everything to make a C header into a C++ header, but conditionally tacking noexcept onto function declarations takes more effort.

Ideally we would fix this upstream and then bring it back here.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.