recovery: use __android_log_pmsg_file_write for log files

- Add call to __android_log_pmsg_file_write for recovery logging.
- Add call to refresh pmsg if we reboot back into recovery and then
  allow overwrite of those logs.
- Add a new one-time executable recovery-refresh that refreshes pmsg
  in post-fs phase of init. We rely on pmsg eventually scrolling off
  to age the content after recovery-persist has done its job.
- Add a new one-time executable recovery-persist that transfers from
  pmsg to /data/misc/recovery/ directory if /cache is not mounted
  in post-fs-data phase of init.
- Build and appropriately trigger the above two as required if
  BOARD_CACHEIMAGE_PARTITION_SIZE is undefined.
- Add some simple unit tests

NB: Test failure is expected on systems that do not deliver either
the recovery-persist or recovery-refresh executables, e.g. systems
with /cache. Tests also require a timely reboot sequence of test
to truly verify, tests provide guidance on stderr to direct.

Bug: 27176738
Change-Id: I17bb95980234984f6b2087fd5941b0a3126b706b