EuiFieldNumber: converted to Typescript

[ffknob]

Summary

Closes #2652
Converted EuiFieldNumber 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]

I left some code commented. I don't know if the goal of that numberOrEmptyString function was to really send some error message back, or only to test the value for number | ''.

If the validation should still be in place, how do you suggest I use this function? (I don't think I can use it to type the attribute in the interface, as it was the case with propTypes definitions)

[thompsongl]

I don't know if the goal of that numberOrEmptyString function was to really send some error message back, or only to test the value for number | ''.

@chandlerprall, what do you think? I'd be comfortable removing numberOrEmptyString entirely and relying on TypeScript for feedback. number | '' is pretty clear.

[chandlerprall]

Using number | '' and removing numberOrEmptyString sounds good to me!

[thompsongl]

Similar changes to what you did with EuiFieldPassword:

Remove the TS reference in src/components/form/index.d.ts line 2:
/// <reference path="./field_number/index.d.ts" />
and then delete the ./field_number/index.d.ts file as it is no longer needed

[thompsongl]

jenkins test this

[thompsongl]

jenkins test this