PackageParser support for flagging manifest entries

This CL adds a flag cache class to PackageParser that is
available during the startup package Parsing, as opposed to
the one in SettingsProvider.

Manifest parsing now calls into this cache to skip the flagged-
out entries

Bug: 297373084
Test: atest PackageParserTest
Test: Manually on a device. Verified that permissions behind a disabled
feature flag were absent. Override the setting for the flag in device
config to enable it, rebooted, then the permission was present.

Change-Id: I8d8ea0a264dfbfd30adf79c6051410cda7bdebbe