[AWARE] Add discovery window period configuration

Discovery window period configuration modifies the duty cycle of
the Aware discovery session. Allowing trade-offs of discovery
latency vs. power.

Add the configuration.

Note: the whole ConfigRequest object is not public (at this point)
so by default so is the new configuration.

Bug: 33552536
Test: unit tests and integration (sl4a) tests.
Change-Id: I16f5c084dbc91431763a81de0a3adfe6f452e44c