Allow devices to specify their own flags by overriding this class.
Additionally, fix a missing PackageManager lookup in getIntent().
Bug: 348647186
Test: launch Settings on Pixel and on AOSP
Change-Id: I2489a64804f068a957f9be3f87847d6911b24447
The new option will only appear if (1) the flag is enabled and (2)
DeviceDiagnostics.apk is landed on the device (which it is by default on
AOSP).
Bug: 309886423
Test: Build AOSP Pixel and launch Settings
Change-Id: If01d231664a301ff289d4da61445bf65a7506fdb