[EuiComboBox] Clearable functionality should work during text search/typing

[cchaos]

At least with single selection turned on, the clearable button only exists when you have an item selected. But to easily clear something that was typed, it would be good to have the clearable button show up before a selection has been made, but when there is text in the input.

There is also a bug where if you clear the current selection by typing to find a new item, the clearable button still exists, but clicking it doesn't actually clear anything.

Screen.Recording.2021-12-21.at.12.18.58.PM.mp4

[cchaos]

The clear functionality in EuiComboBox does not clear invalid options:

I discovered this through this bug report: elastic/kibana#120609

We have a reset button that "resets" the selectedOptions prop. However, this does not clear invalid options either. I'm not sure if fixing the clear problem will fix our problem or if we need a clear handler?

Originally posted by @stephmilovic in #5500

[JasonStoltz]

@cee-chen Any idea if this will be fixed by #2841?

[cee-chen]

No, EuiComboBox will likely need its own custom input still, so will need some manual fixing.

[teresaalvarezsoler]

I cannot find this experience in the dashboards/lens/discover UI anywhere. Do you know if this has been implemented anywhere? Otherwise I think it's fine postponing it until there is a real use case.

[JasonStoltz]

@timductive Did you have a specific location this is used in mind?