Adds new flags LINK_PADDED and INSTR_BRANCH_PADDED and uses them to mark exit cti padding added for safe patching. Reads the link flag in decode_fragment() to remove the padding during trace building. This avoids prior trace barriers from extra basic block exits from inlined syscall exits, rseq mangling, and client changes.
Removes the option and stats around -pad_jmps_mark_no_trace which is no longer needed.
Tested on the linux.rseq test which now successfully traces through the rseq mangling.
Fixes #4038 (closed)