Added State to remember app shortcuts modified

Adding a state to recall app shortcuts customized by the user in the
current customization session. This is ground work for custom shortcut
sorting logic in follow-up CLs.

Test: ShortcutCustomizationModeRepositoryTest
Test: ShortcutCustomizationInteractorTest
Flag: com.android.systemui.extended_apps_shortcut_category
Bug: 407506063
Change-Id: Ieb444f5148535f9776abd0dece90bc3be6fcb01e