Move BugreportPrefs constants to shared location between sysui and shell

bug:380825247
Manual test:
	- M -> to build
	- sh vendor/google/tools/flashall -> to install changes
	- Set watch to test mode: adb shell am broadcast -a com.google.android.clockwork.action.TEST_MODE
	- Select Take bug report and press in details when finished

Flag: EXEMPT refactor

Bugreport: https://drive.google.com/file/d/1vCUk5Q18jWH2IPEbhTBUCZf0K3WE74LD/view?usp=sharing&resourcekey=0-qTNzJx3VoCf3lpsUEBCUIg
(cherry picked from https://partner-android-review.googlesource.com/q/commit:beeaf50d15a1bafb48f006b7cd77393d04180b3f)
Merged-In: Id59ecadbecd84f79474184c0110aa6536ec8abf4
Change-Id: Id59ecadbecd84f79474184c0110aa6536ec8abf4