[Accessibility] A <label> for time bucket size selector on discover

[PhilippBaranovskiy]

Fixes #19448

Summary

Axe analyzing tool warns that form element should have an appropriate labels event if they are not a part of <form>.
Here I've replaced <span> with <label for=""> and placed id attribute to <select>.

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• This was checked for cross-browser compatibility, including a check against IE11
• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[elasticmachine]

Pinging @elastic/kibana-app

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[vitalics]

a common issue with the previos master branch. Could you please update your source code. This issue was already solved

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[PhilippBaranovskiy]

@vitalics, updated and checked, please have a look one more time, please.

[bhavyarm]

@rockfield can we get this label of time interval box to read as timespan? Is that possible? Right now screenreader reads it as "checkmark second".

[vitalics]

code LGTM for me

[PhilippBaranovskiy]

@rockfield can we get this label of time interval box to read as timespan? Is that possible? Right now screenreader reads it as "checkmark second".

@bhavyarm let's create another issue and update that <select> later?
Here the one: #38794
If you think it's good to add some further details, please update the ticket.

[PhilippBaranovskiy]

@bhavyarm does it work?

[bhavyarm]

LGTM as we are fixing the aria-label in a different PR