Split p_search_cback into device and service search callbacks

Each occurence of p_search_cback will be split in separate patch, to
ease reviewers. Therefore, this patch alone does not compile.

Wether device or service search is interested in given event is
determined by checking the btif_dm_search_services_evt and
btif_dm_search_devices_evt.

Flag: exempt trivial refactor
Bug: 330675788
Test: mma -j32
Change-Id: I7e73dce683e5cedaf8abb6963ee139700d3f377d