[ML] Single day / date range / time range tabs not accessible via screen reader

[aphelionz]

Steps to reproduce (assumes ChromeVox or similar)

(Presumes a job has already been created in Machine Learning)

1. Open Kibana in a new tab
2. Tab to Machine Learning
3. Tab to Settings
4. Tab to Calendar Management
5. Enter a calendar ID, description, job name, and group name
6. Tab to New Event, Press Enter
7. Try to tab to the single day / date range tabs

Actual Result
8. User cannot reach the tabs via the keyboard

Expected Result
8. User should be able to navigate to the tabs using the keyboard

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

[elasticmachine]

Pinging @elastic/ml-ui

[peteharverson]

A possible solution is to convert the current tabs into buttons.

[alvarezmelissa87]

Fix: #23832