[CFIFixup] Add frame info to the first block of each section (#113626)
Now that `-fbasic-block-sections=list` is enabled for Arm, functions may
be split aross multiple sections, and CFI information must be handled
independently for each section.
On x86, this is handled in `llvm/lib/CodeGen/CFIInstrInserter.cpp`.
However, this pass does not run on Arm, so we must add logic for it
to `llvm/lib/CodeGen/CFIFixup.cpp`.