Improve settings cold start latency.

- Move view initialization from onViewCreated to onCreateView. This
  doesn't really improve anything, it simply aligns the code more
  with view's lifecycle management.
- Move dashboard category init into background. The init contains logic
  invoking packageManager, which can be very expensive.
  - Remove any call to DashboardFeatureProvider from SummaryLoader, and
    delay the getCategory call until someone calls setListener().
  - call updateCategory() from background thread.

Test: rerun app launch test. Avg latency drops back to pre-suggestion-v2
      level.
Test: robotest
Fixes: 68761512

Change-Id: I5ec85af08e7b610786e439bda93b3651f5975593