Adds timeout mechanism for soft AP when no clients

Sets a timer to shut soft AP down whenever there are no connected
clients. Cancels the timer if a new client get connected. This feature
will be enabled/disabled by a toggle control from Settings UI. Timeout
duration is configurable as an overlay setting.

Bug: 68712445
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: manual test on device (default 10 minute timeout)
Change-Id: I38a90fe327982d5493d55f6322c50ed86c48fa52
4 files changed