Add Zicfilp extension

[ved-rivos]

Specification: https://github.com/riscv/riscv-cfi/blob/main/cfi_forward.adoc Tests: https://github.com/riscv-non-isa/riscv-arch-test/pull/413

[jrtc27]

It should not take 15 commits like that to add this extension. Please condense into a sensible history.

[ptomsich]

It should not take 15 commits like that to add this extension. Please condense into a sensible history.

The part that Jessica didn't make explicit is: we use a "rebase and merge" strategy and don't squash your history when merging, so your history should be considered part of the submission.

[ved-rivos]

It should not take 15 commits like that to add this extension. Please condense into a sensible history.

Sorry, that the commit history was nonsense. I have squashed some of the commits. Let me know if it makes sense now.

[github-actions[bot]]

Test Results

712 tests  ±0   712 :white_check_mark: ±0   0s :stopwatch: ±0s   6 suites ±0     0 :zzz: ±0    1 files   ±0     0 :x: ±0 

Results for commit 1056a624. ± Comparison against base commit 40ed0c5b.

:recycle: This comment has been updated with latest results.