Include all flags in our flag list.

This improves the use of reflection to include all the flags listed
in Flags.kt. One interseting finding: I can't figure out how to
get the value of a field marked with just `@Keep`. It needs to
also have `@JvmField` or not have any annotations at all.

More changes to this code will come in follow up cls, using string
names where appropriate, but this improves existing functionality.

Key takeaways:
- Reflection is terrible
- Reflection in Kotlin is worse
- Reflection on `object` instances is worse still
- Reflection mixing Java with Kotlin follows the trend line
- Reflection on annotated fields is nigh impossible

Bug: 249121873
Test: adb shell cmd statusbar flag
Change-Id: I69a96501876b01570233c3fd80b6bc7334d9fe73