Use equals() to check equality of PictureInPictureParams.

Introduce equals() method to PictureInPictureParams and RemoteAction.

Also makes a dup of PictureInPictureParams when filling task info to
avoid the same instance being updated later which will interfere
equality checks.

Bug: 174786192
Test: PIP on YouTube looks OK.
Change-Id: Ifd8534589d784719dfd5f9b37412ca8779a46983