Introduce isTv to adapt services to Android TV uses

This variable is intended to be used as part of the startOtherServices
method of the system server much like `isWatch` is used now in order
to selectively skip starting system services, which are not relevant to
the operation of Android TV.

Test: make
Bug: 264411203
Change-Id: Ife21ac60e11d6669954dc0f77b2c85d0149d2d7b