Add set supported value debug command.

Add debug command to ref VHAL to allow setting min/max value and
supported values list for the test vendor property. The command
also triggers supported value change event so that we can test
the subscription logic.

Flag: EXEMPT HAL change
Test: atest FakeVehicleHardwareTest
Manual test using KS, verify we see the supported value change event.
Bug: 382563296

Change-Id: I7ec791b1ee8e6cade4e267b55e4b58e1d3a9e49c