This PR implements the emitting of the post-link CFG information in PGO
analysis map, as explained in the
[RFC](https://discourse.llvm.org/t/rfc-extending-the-pgo-analysis-map-with-propeller-cfg-frequencies/88617).
This is enabled by a flag `pgo-analysis-map-emit-bb-sections-cfg`.
This PR bumps the SHT_LLVM_BB_ADDR_MAP version to 5.
Also includes some refactoring changes related to storing the CFG in the
Basic block sections profile reader.