Open activity directly from notification (inbound transfer)

When user clicks the OPP notification for inbound transfer,
this CL makes the activity start directly from the notification.

Previously the intent was sent to BluetoothOppReceiver first,
which added noticable delay before launching an activity.

Since inbound and outbound transfer used almost same intents whose
only difference is their intent extras, this CL makes the intent
action be different for better code readability.

Bug: 319050411
Bug: 318610752
Test: atest BluetoothOppReceiverTest
Test: manual, after receiving a file via Bluetooth, click the
      notification titled "Bluetooth Share: Received files".
      There should be no lag when opening the activity
      "Inbound Transfers".
Change-Id: Ia24f19bb7d854eca1f9ea1b107f06287003f5bfe