Remove TS types & interfaces from ES exports

[chandlerprall]

Summary

Fixes #1376. This extends our typescript->proptypes babel plugin to also remove any types or interfaces from ExportNamedDeclarations e.g. export { Foo, Bar } & export { Foo, Bar } from './source';. Added this functionality to the existing plugin for two reasons: 1. no build tooling in TS or Babel performs this transformation 2. our plugin already tracks variable type information across imports.

I tested this change in create-react-app by generating an npm module tarball with npm pack and adding the contents of that tarball as a dependency in a new CRA project.

Checklist

- [ ] This was checked in mobile
- [ ] This was checked in IE11
- [ ] This was checked in dark mode
- [ ] 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
  - [ ] This was checked against keyboard-only and screenreader scenarios
  - [ ] This required updates to Framer X components

[chandlerprall]

this enter: {} block is the same as Program was previously, just indented another level. The exit block below is new.

[thompsongl]

Kibana integration checks out: built & linked EUI still passes tests and runs locally

[thompsongl]

Verified export/import resolution via the same CRA integration mentioned in the issue and description for this PR (tarball dep and @elastic/ui import target in js).

[chandlerprall]

Did a final check, diffing the contents of es and lib build directories with and without this change. Confirmed that this only affects the types exported from icon and also the rgbDef type exported from color. Fixing the changelog conflict then will merge.