EuiSelect: converted to Typescript

[ffknob]

Summary

Closes #2655

Converted EuiSelect to Typescript.

Checklist

• Check against all themes for compatability in both light and dark modes
• Checked in mobile
• Checked in IE11 and Firefox
• Props have proper autodocs
• Added documentation examples
• Added or updated jest 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

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[ffknob]

Looks like there is no readonly attribute for the SelectHTML element... Typescript complained and I then exchanged it for a disabled one. Any suggestions?

[chandlerprall]

Disabling the element will exclude it from inclusion in POSTs, which would be a breaking change. There's another option presented in https://stackoverflow.com/a/23428851 , @cchaos thoughts on the design side here?

[cchaos]

My thoughts are that allowing for readOnly was a bug. The select element inherited some styles that came with the readOnly state, but the element itself is actually still interact-able.

Therefor readOnly was incorrect and removing it as a prop would be a bug fix. I don't think the intention for consumers to add readOnly is the same as disabling.

[chandlerprall]

@ffknob please go ahead and remove the readOnly prop; we'll continue to allow consumers to pass disabled={true} to the component via ...rest

[ffknob]

@ffknob please go ahead and remove the readOnly prop; we'll continue to allow consumers to pass disabled={true} to the component via ...rest

Removed the prop and related tests.

[chandlerprall]

Should be the last one

[chandlerprall]

Suggested change

	text: string;
	text: React.ReactNode;

[chandlerprall]

jenkins test this