added Logic to convert UI key event to shortcut key models

This is background work for capturing user's selected key combination
for a shortcuts

Test: CustomShortcutCategoriesRepositoryTest
Flag: com.android.systemui.keyboard_shortcut_helper_shortcut_customizer
Bug: 373638584
Change-Id: I4c1878187a682cad24b995e83946f1d7aeda1e4a