Update AM related owners

- Mark app start info related files to be owned by performance owners.
- Mark app exit info related files to be owned by AM.
- Mark activity manager flag config to be owned by AM.
- Add myself to performance owners.
- Cleanup owners that were described as specific to certain areas but actually covered everything.
- Remove last resort from default reviewer Amith.

Test: presubmit
Bug: EXEMPT - owners change
Flag: EXEMPT - owners change
Change-Id: I74916f336ac1fb51b3136983875eeb0da1da4836