Misc cleanup on AndroidManifest.xml

- Add a few activities to widget list. These are more commonly
  used settings, so adding them to widget list for easier access.
  - Storage
  - System
  - About phone

- Remove useless intent-filters from AndroidManifest.
  - If the intent-filter is just action MAIN and category DEFAULT, it
   doesn't do anything.

Bug: 74806595
Test: visual
Change-Id: I5d80bc6c88f7bf60adabac872e92b72b341b97e6