[EuiDatePicker] Better handle onBlur callback

[thompsongl]

Summary

Addresses a specific bug whereby wrapping EuiDatePicker in EuiToolTip will cause the tooltip to never close once opened: https://codesandbox.io/s/nervous-smoke-kk5ys
The root problem was that provided onBlur callbacks are simply ignored, and as such the solution applies more broadly to all blur event scenarios.
The intended behavior is that onBlur callbacks only get called when the entire component loses focus. That is, if either the input or any element in the popover has focus, we treat that as internal focus transfer and not blur.

Additional update includes a change to EuiToolTip so that is does not omit configured onBlur and onFocus callbacks on the child component.

Checklist

• Check against all themes for compatibility in both light and dark modes
• Checked in mobile
• Checked in Chrome, Safari, Edge, and Firefox
• Added or updated jest and cypress tests
• Checked for breaking changes and labeled appropriately
• Checked for accessibility including keyboard-only and screenreader modes
• A changelog entry exists and is marked appropriately
• Reverted 70dc65b

[1Copenut]

I did a quick run through with Safari and Chrome, looking specifically at keyboard and click navigation patterns. They all worked well, and honored the blur() event to hide the tooltip.

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5441/

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5441/

[1Copenut]

I've taken a pass through with Firefox, Chrome, and Edge on MacOS locally to test for consistent behavior with the tooltip. All were behaving as expected. LGTM!

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5441/

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5441/

[breehall]

This looks good, Greg! I ran through the changes in the PR preview and compared it to the current version of the docs. The updated onBlur functionality creates a clean experience.

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5441/