Use USE_BUGREPORT_API flag from FeatureFlagUtils

To avoid flag duplication, this flag is moved to FeatureFlagUtils.java
where other callers can also use this flag. Using this flag's value from
FeatureFlagUtils instead of the local FeatureFlag file in Settings.

Bug: 136548292
Test: Settings can still access this feature flag as before
Test: Builds and API workflow gets triggered by turning on the flag
Change-Id: I60e4d96033219c934a43e728705fee93e338d60e