Update physical keyboard shortcut for taking bugreport.

The shortcut moves from shift+MENU to META+CTRL+Backspace. Remove
the legacy handling of the shift+MENU combination as it doesn't
work anyway.

Fixes a test issue where using the flag checking rule would trigger an
assert from AccessibilityManager. The flag checker activates UI
Automation which in turn, activates the Accessibility Service. Prior
to this change, the tests relied on the fact that Accessibility was off
by default. To work around this, we disable AccessibilityManager
explicitly in TestPhoneWindowManager.

Bug: 335607520
Flag: com.android.server.flags.new_bugreport_keyboard_shortcut
Test: atest ModifierShortcutTests WmTests:com.android.server.policy.ShortcutLoggingTests
Change-Id: Icdcf49c6d20bded85a4376fa731799fbe3060d51