Address review comments for fade manager configuration API

- For easier reference by clients, make default fade out and
  fade in durations queriable through static methods.
- Remove IntDef references from JavaDoc. Add these definitions
  directly on the parameter itself.
- Remove redundant Null pointer exception details from the
  JavaDocs, as this is documented by the @NonNull annotation.
- Added explanation to clarify the term 'offending' players.
- Remove FADE_STATE_ENABLED_AUTO since no custom behavior
  available at this time.

Bug: 318430127
Bug: 319321475
API-Coverage-Bug: 308666800
Test: atest FadeManagerConfigurationUnitTest

Change-Id: I97011ca3f493f28600f9779e771646182acdc6e7