Update ComputerControl Activity policy

- Only allow launching applications specified in the ComputerControl
  session parameters targetPackageNames
- Throw on session request if the targetPackageNames includes an invalid
  package that is not allowed to be automated

Bug: 437849470
Test: atest ComputerControlSessionProcessorTest
Flag: android.companion.virtualdevice.flags.computer_control_activity_policy_strict

Change-Id: Ia8d96c833cc07d7b65e71f44c4164ed7c3007530