WifiDiagnostics: Flush HAL ring buffer to files

To help diagnose problems in connection problem.
Flush ring buffer to files when trigger bug dump.

Bug: 118854557
Test: Run unit tests, OK (3025 tests)
Test: Trigger bugreport.
Change-Id: I055cb570e3597ef564e1f78a2cd38985b2f6e07c
9 files changed