wifi(implementation): Clear the chip immediately on IWifi.stop()

Currently, we wait for the legacy HAL callback to complete to clear and
invalidate the chip objects and it's derivatives. This may cause us to
access the wifi legacy HAL in a indeterminate state (as it's processing stop)
on subsequent HIDL calls.
So, clear up the chip object and derivatives immediately after we
process the stop to prevent any subsequent calls from sneaking in.

Also,
Added a couple of logs when wifi HAL is started/stopped to help debug
such issues later.

Bug: 36026601
Test: Turn on/off wifi and switch to softap mode multiple times.
Change-Id: Id5c2c9a90a335b2de4ae331ac8610b1a4e7875da