* Log when the user's lockscreen password has been changed, together
with the new password's complexity level.
* Also expose SecurityLog.writeEvent() as SystemAPI, as some
mainline modules (WiFi etc) will start emitting security events.
Bug: 194988881
Test: atest MixedDeviceOwnerTest#testSecurityLoggingWithSingleUser
Test: atest OrgOwnedProfileOwnerTest#testSecurityLogging
Change-Id: I2da4fdd15f85fab9244a978be7b1dafb4a82d190