[PA/shim] Guarantee tail call optimization

Add MUSTTAIL macro (which is replaced with [[clang::musttail]]) and
use it wherever possible in AllocatorShim's dispatcher chain.

TCO has some requirements for arguments of caller and callee, but
the dispatchers meet it as caller and callee take exactly the same
argument types.

Bug: 40944045, 351974425
Change-Id: I8d74afd6786e6891beb6a1071da54eb936935bfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5686903
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Mikihito Matsuura <mikt@google.com>
Cr-Commit-Position: refs/heads/main@{#1325017}