[EuiFieldNumber] Update native validity state on blur & report/surface native validation messages

[cee-chen]

Summary

closes #6747

As @dej611 noted in the linked issue, several browsers (namely Safari) do a really poor job of surfacing their native validity messages, meaning that we're rendering inputs as invalid/with a scary warning icon without actually telling users why.

The native browser way of handling this would be to use the reportValidity API, which renders minimally intrusive browser tooltips with the native error messages, without requiring a hover action from users.

If consumers would prefer to render their own error messages via <EuiFormRow error={}>, they can do so and turn off the browser-level invalid reports via reportNativeInvalidity={false}.

Chrome/Edge:

Firefox:

Safari

(Safari's validation is still kinda garbage but a bit better than before)

QA

General checklist

• Checked in both light and dark modes (native browser reporting follows system darkmode, not EUI darkmode)
• Checked in Chrome, Safari, Edge, and Firefox
• Props have proper autodocs (using @default if default values are missing) and playground toggles
• Added documentation
• Added or updated jest and cypress tests
• Checked for accessibility including keyboard-only and screenreader modes
• A changelog entry exists and is marked appropriately

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_6758/

[cee-chen]

Putting a stop to this - in my SR/keyboard testing I unfortunately discovered webkit browsers autofocus inputs when reportValidity is called, meaning that invoking the validity check/report onBlur causes focus to be trapped on the input 💀