mcp: Add implementation of Generic Media Control Service

Media Control Profile implements the Generic Media Control Service
and media playback controls by hooking into the Media Session Framework.
It represents the global media state and allows to controll it,
similar to AVRCP.

Bug: 150670922
Tag: #feature
Test: atest McpServiceManagerTest McpServiceTest MediaControlProfileTest
Sponsor: jpawlowski@
Merged-In: Ie2cd94f050251cf7df2c65cfd46c312bcf303b5f
Change-Id: Ie2cd94f050251cf7df2c65cfd46c312bcf303b5f