Simplify and fix resolveIntent implementation

- `exportOnly` is false only when resolving on behalf of system_server,
  which is automatically handled in `filterNonExportedComponents`, so
  there is no need to additionally pass this boolean.
- `resolveIntentExported` is unnecessary as functionality is duplicated
- PM#resolveIntent() should follow normal intent resolving process and
  return the correct Activity. The implementation before this CL is
  incorrect (`exportOnly` is set to false).

Test: TH
Change-Id: I01b3295295b4b2dbdced54971b525aaa6126ed01