persist ringbuffer to flash when vendor hal stops

Need to write ringbuffer to flash or else the data become lost.
Also added logic to make sure ringbuffer files over the max limit
get deleted.

Bug: 78025947
Test: compile
Manual test:
flash to device
connect to wifi network
toggle wifi off and observe that ringbuffer files are persisted
keep toggling until the number of files get over the max allowed amount
and verified that old files got deleted

Change-Id: I7d6cff81cf5400a79d1c93a1e12e72fd1a766dad