Connected MAC Randomization Metrics Proto

1) Add "is_mac_randomization_on" that indicates if Connected MAC
Randomization is turned on/off when the proto is created.

2) Add "TYPE_MAC_CHANGE" as a new trigger event for StaEvent. This will
occur whenever we are dynamically changing the MAC address for Connected
MAC Randomization.

Bug: 73666905
Test: Unittest.
Change-Id: Ifef0908f668e39531ebe5a38588f8e3713c047a9