Use POWER_MENU_LOCKED_SHOW_CONTENT in wallet

Use POWER_MENU_LOCKED_SHOW_CONTENT to control lock screen behavior for
the Quick Access Wallet.
Do not provide Intents that will fail to start an Activity.
Update comments.

Bug:155232731
Bug:155186709
Test: manual
Test: atest CtsQuickAccessWalletTestCases

Change-Id: I78e5355a69d666aee6dd122389edabed170f07b2