[X86] Set frame-setup/frame-destroy on prologue/epilogue CFI instructions

This approach is used by AArch64/RISCV to make frame-setup/frame-destroy
instructions contiguous instead of being interleaved by CFI instructions. Code
checking `MBBI->getFlag(MachineInstr::FrameSetup) || MBBI->isCFIInstruction()`
can be simplified to just check FrameSetup.

This helps locate all CFI instructions in the prologue, which can be handy to use
.cfi_remember_state/.cfi_restore_state to decrease unwind table size (D114545).

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D122541