[AMDGPU] Add pal metadata 3.0 support to callable pal funcs (#67104)

PAL Metadata 3.0 introduces an explicit structure in metadata for the
programmable registers written out by the compiler backend.
The previous approach used opaque registers which can change between different
architectures and required encoding the bitfield information in the backend,
which may change between versions.

This change is an extension the previously added support - which only handled
entry functions. This adds support for all functions.

The change also includes some re-factoring to separate common code.