Add VUR to VHAL interface.

Add enableVariableUpdateRate to subscribe options and
supportVariableUpdateRate to VehicleAreaConfig. If variable update
rate is enabled, VHAL will only send property change events for
continuous property if the property's value changes. This is for
improving performance and not send duplicate events.

Test: m
Bug: 306754638
Change-Id: Ic0d1ec2ebbf8ed6c26da3f3b820ac85e9c345b2c