[Device Supervision] Create a proxy activity to set screen lock

The proxy activity could start set PIN activity with specific user and send result as callback, which PreferenceLifecycleContext does not support. This could be a shared proxy activity for change PIN, PIN recovery etc.

Bug: 410122671
Flag: android.app.supervision.flags.enable_supervision_settings_screen
Test: atest SupervisionCredentialProxyActivityTest
Change-Id: I3e9fde67b88e6fd9e220d9808f10234c01cb19d6