Check if autocomplete behaviour is still connected

While working on https://github.com/flutter/devtools/pull/6677

I noticed that we have autocomplete behaviour in the widget inspector search field.

I've never once seen it pop up though, so I wonder if maybe it got disconnected at some point.
If so we should discuss reconnecting it.
While discussing this we should discuss it's behaviour. If possible it would be nice if the user could use enter and shift+enter to navigate the search results. So we could tweak the autocomplete indexing while we are in the area.(See https://github.com/flutter/devtools/issues/6864)

https://github.com/flutter/devtools/blob/master/packages/devtools_app/lib/src/shared/ui/search.dart#L1253