[EuiSuggest] euiPanel should not be rendered in case of no suggestions

[alexwizp]

Currently if we pass [](Empty array) into suggestions property we anyway render euiPanel:

It causes some issues:

1. wrong animation effects

2. keyboard navigation issues. If user press Tab button, we set focus into euiPanel instead of next form control

[thompsongl]

Would it make sense to have some kind of empty state or prompt in the panel instead of hiding it?
For instance, EuiComboBox is similar and provides feedback to the user that no options match:

Related: #4302

[cchaos]

I think there's some overall component confusion as to the use-case for EuiSuggest. Most of these new issues revolving around EuiSuggest are trying to replicate functionality that already exists as a part of the EuiComboBox. I added this comment to the Draft PR on the Kibana side to start a discussion as to whether these should be aligned or using EuiComboBox is the better component.

[elizabetdev]

I agree with @cchaos. The purpose of the EuiSuggest is different than the EuiComboBox. If we want to match options we should use EuiComboBox where if something isn't matched the user is informed that nothing was matched.

For the EuiSuggest the suggestions should only appear if what we typing has a suggestion. If something doesn't match any suggestion the popover shouldn't open.

With that said, I think if we pass an empty array to EuiSuggest a blank popover shouldn't open and this PR makes sense:
#4349