Update documentation for initialize()

Updates the documentation for the initialize() function and defines
the requirements for using the Event FMQ's writeBlocking function
which requires both a read and write notification.

Also adds requirement for the Sensors HAL to cleanup active sensor
requests and direct connections whenever initialize is called.

Bug: 120857563
Test: Builds
Change-Id: I11c8f7404d27e9ab21f9314523faebc1970b9f0c