[libc] Switch to use a macro which does not insert a section for every libc function.

Summary:
The new macro also inserts the C alias for the C++ implementations
without needing an objcopy based post processing step. The CMake
rules have been updated to reflect this. More CMake cleanup can be
taken up in future rounds and appropriate TODOs have been added for them.

Reviewers: mcgrathr, sivachandra

Subscribers:
GitOrigin-RevId: a0b65a7bcd6065688189b3d678c42ed6af9603db
147 files changed