[JITLink][PowerPC] Add TOC and relocations for ppc64

This patch builds TOC and adds common relocations for ppc64.

To build TOC, sections belong to TOC are merged into one section, serves as GOT and small data accessing.

Relocations commonly seen in local function call, external function call and global variable reference are added.

References
- https://youtu.be/i-inxFudrgI
- https://maskray.me/blog/2023-02-26-linker-notes-on-power-isa
- https://openpowerfoundation.org/specifications/64bitelfabi/

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D154198