Enables the diagnostic option -steal_reg_at_reset for AArch64, generalizing the existing ARM code.
Switches -reset_at_fragment_count to work in release build by using the sum of the release stats num_bbs and num_traces.
Adds a release-build syslog for an informational notification when any reset occurs.
Adds a test of -steal_reg_at_reset.
Issue: #1569