Add dialog title for shortuct customization dialogs

This is needed for accessibility, otherwise accessibility will announce
"SystemUI" when the dialogs are opened

Test: Manual - use talkback , open add/remove/reset shortcut dialog and
ensure there is a meaningful description announced instead of "systemUI"
Flag: com.android.systemui.keyboard_shortcut_helper_shortcut_customizer
Fix: 390316097

Change-Id: I30b2eda02089eebdaea41aba94ddfebaf09c95cd