[Clang] Deprecate `__is_trivially_relocatable` (#138835)
The C++26 standard relocatable type traits has slightly different
semantics, so we introduced a new
``__builtin_is_cpp_trivially_relocatable`` when implementing trivial
relocation in #127636.
However, having multiple relocatable traits would be confusing in the
long run, so we deprecate the old trait.
As discussed in #127636
`__builtin_is_cpp_trivially_relocatable` should be used instead.
---------
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
