[ML] Create New Job - Job Groups tags input not tabbable

[aphelionz]

Steps to reproduce (assumes ChromeVox or similar)

1. Open Kibana in a new tab
2. Tab to Machine Learning
3. Tab to "+ Create New Job" button
4. Press enter
5. Choose the first saved search
6. Choose the "Single Metric" wizard
7. Fill in aggregation, field, and bucket span enough to show the graph and lower fields
8. Tab to job groups
9. Type "Test" and hit enter to create a new test tag
10. Press shift+tab to try and select the X" inside the just-created tag,

Actual Result
11. The tag is not accessible via keyboard

Expected Result
11. The tag, or at least the "delete tag" X button, should be accessible via keyboard

Category: #18866 Kibana 6.3 Meta Issues
Relevant WCAG Criteria: 2.1.1 Keyboard

[elasticmachine]

Pinging @elastic/ml-ui

[peteharverson]

A possible solution is to swap out the current ui-select control for an EUI input. Note the job wizard pages are on the list for needing conversion to EUI / React (see #18374).

[peteharverson]

This functionality should be added as part of the new EUI / React based job wizards.