Adds translation of the save of input registers to rseq sequences.
This fixes a hang on detach in the api.ir test on AArch64, which we remove from the flaky list here.
Manually tested by running api.rseq 200x on the Jenkins machine. Previously the test failed every single time there.
Issue: #4923 (closed), #4316 (closed), #4669 Fixes #4923 (closed)