contexthub: create a package and add OWNERS file

- For newer API types in contexthub, we would like to create a
  package android.hardware.contexthub.
- Assign original owners to the new package, without Hub being an required word.

Test: Build
Flag: EXEMPT, OWNERS file only change
Bug: 375487784
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:eb3c69a5bf0f40b04c9bf5d0c570a546b93ade71)
Merged-In: I27f815021691ce0e5a79c16cb5877276eaaabacb
Change-Id: I27f815021691ce0e5a79c16cb5877276eaaabacb