Add waits for job toolbar icon appearances

Sometimes there's a slight delay before the toolbar icon appear, so wait
before checking the icon's properties.

Bug: 430400772
Test: atest -c 'DocumentsUIGoogleTests:com.android.documentsui.JobPanelUiTest'
Flag: com.android.documentsui.flags.visual_signals_ro
Change-Id: I5793965360bf9236d7e22ffd591c1115a27942b1