contexthub: create basic findEndpoints EndpointInfo API

- Create a basic parcelable for EndpointInfo.
- Create a basic ContextHubManager.findEndpoints(long) for retrieving
  particular endpoints with known statically generated known IDs.
- Create a stub implementation in ContextHubService for this API
- Add OWNERS for contexthub package

Test: manual
API-Coverage-Bug: 377554469
Bug: 375487784
Flag: android.chre.flags.offload_api
Change-Id: I5abec4c4e40d0df6ac72d41ba0d80b8ba240b686