BTTestApp: Porting BTTestApp on Android P.

 This patch enables BTTestApp in Android P release code.

 Change-Id: I0d60d313e9e125dc84002cdf80de35366aa5d85d

 BTTestApp: Dynamic A2DP Role switch and AVRCP controls

 This change contains support to switch A2DP role from
 A2DP Source to A2DP Sink and vice versa. Also change
 contains support to send AVRCP passthrough commands
 from BTTestApp.

 Change-Id: If272a3a74cc60b2052da2b9bb6f1da7eae44ddb2

 BTTestApp: New interface for AVRCP CTRL

 This change contains to support Cover Art.

 Change-Id: I6ac6b1abbee7dc95e79c8004dd83c91f9bf96e7a

 BTTestApp: Fix duplicate cover art issue

    Use case:
    1. Pair and connect DUT with remote.
    2. Play any song which has cover art.
    3. Cover-art is displayed correctly.
    4. Play a song which does not have cover art.

    Result:
    Even though song in step 4 is played,
    cover art of song in step 2 is displayed on DUT.

    Fix:
    Clear previous bit map when we receive invalid
    broad cast of specific cover art.

 Change-Id: I72d4def06d8507ede1df2627b46b4c5df823b420

CRs-Fixed: 2215066
Change-Id: I7942e80f70b5bc6bb54fd7d75794b443f5b891cd