Remove unused broadcasts/functions/variables from Shell

Bugreport is now triggered using API and not via broadcasts from
dumpstate. As migration to API flow is stable, we can remove methods and
broadcasts that were used in non-API bugreport flow. Now, callbacks are used
for communication between dumpsate and Shell instead of broadcasts.

* Remove BugreportReceiver.java as it used to handle BUGREPORT_STARTED and
  BUGREPORT_FINISHED intents which are not required by Shell anymore to
  track bugreports.
* Remove RemoteBugreportReceiver.java as it used to handle
  REMOTE_BUGREPORT_FINISHED intent which is not required by Shell
  anymore.
* Remove methods that were being used when processing these broadcasts.
* Remove pid as that is not used anymore.
* Since Shell owns the file now, don't need mTempName, mSavedName,
  onFocusListener and disable file name after the bugreport is finished.
  File name can be sanitized and updated even after bugreport finished.

Bug: 136066578
Test: Build and flash. Interactive/Full bugreports from Settings/Power button.
Test: Rename workflow for interactive bugreports works as expected.
Test: * Build and flash
      * Install TestDPC
      * Make it device owner
      * Take a remote bugreport. Works as expected

Change-Id: I5e0f829631cb63074c41c914236e78abe95ba162