Disable lockscreen shortcuts when the user enters lockdown mode

When lockdown mode is triggered, disable the lockscreen shortcuts until the user has left lockdown mode

Bug: b/285014861
Test: atest KeyguardQuickAffordanceInteractorTest.kt
Test: manual - while on lockscreen with quick affordance visible, enable lockdown mode. Observe the quick affordance becoming hidden. Unlock device, go back to lockscreen, and observe the quick affordance return.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:09c1367cc5c8c7d63ed5022b552c79f72a87b61e)
Change-Id: I7755cf17893e3f98aa66640d68c43bba8bbe7459