DatePicker: datepicker_instActive released on instance destroy

Fixes #10668
Closes gh-1362
Autocomplete: Remove duplicate array key in demo

Ref gh-1363
Demos: Remove duplicate CSS properties

Closes gh-1363
Dialog: Remove leftover backcompat flag in tests
Core: Removed .focus( delay )

Fixes #9649
Core: Remove .zIndex()

Fixes #9156