Address API review feedback for AmbientContext. Add shell method for more test coverage. Do not unregister request from the same client and delegate to AiAi to handle it.

Test: CTS tests
Bug: 219740201
Change-Id: I8fa9df9cab9965d84d301760f4f7fba08dc44f54
(cherry picked from commit 542fc25dffb02f2c794f6c952027a8b6ca5daebe)
6 files changed