Fix lint warnings in KeyguardUpdateMonitor

Summary of changes:
  - Mark final fields final
  - Move final fields together in one block
  - Remove explicit type specification for generics
  - Convert new Runnable to arrow function
  - Make BiometricManager a local variable in the constructor
  - Change android.annotation.Nullable/NonNull to androidx.annotation.* as Dumpable uses androidx.* and using android.* cause warnings for `dump()` method

Bug: 249467771
Test: atest KeyguardUpdateMonitorTest
Change-Id: I71eb6e23b479a076c3d45dd7492238df41f05440