[EuiSuperDatePicker] Add onRefresh handler

[sorenlouv]

When setting the refresh rate on EuiSuperDatePicker it should keep track of the interval, and call the onRefresh handler whenever the interval fires.
This will save consumers the hassle of implementing this logic themselves.

Checklist

• Any props added have proper autodocs
• Documentation examples were added
• A changelog entry exists and is marked appropriately
• This was checked for breaking changes and labeled appropriately
• Jest tests were updated or added to match the most common scenarios

[sorenlouv]

@nreese How do you suggest we document this feature?

[nreese]

How do you suggest we document this feature

@cchaos and @chandlerprall any thoughts on how best to document?

[cchaos]

Move the EuiSuperDatePicker to it's own page and split up the examples to address all these edge cases.

[sorenlouv]

Move the EuiSuperDatePicker to it's own page and split up the examples to address all these edge cases.
@cchaos

Is this a refactor of the EuiSuperDatePicker docs, or just for the new onRefresh prop I'm adding? Not quite sure how much is expected of me to land this PR.

[sorenlouv]

Feedback addressed.

[cchaos]

Thanks! There's just a few outstanding items in the PR checklist to cover, like a changelog entry.

[nreese]

lgtm
code review