Convert loading components to TS, fix ie11 shadow

[snide]

Summary

Fixes #1440
Fixes elastic/kibana#25584

Converts the loading components over to TS and addresses a minor IE error

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

[cchaos]

Did a quick code review. Had a few suggestions/questions but mostly looks right.

[snide]

@cchaos @chandlerprall OK. Ready for another round. Tests added and snippets added as well.

[cchaos]

Code looks good, checked in IE, chrome, and FF. I did notice one weird issue in FF:

But we can address that later?

[chandlerprall]

Changes LGTM; tested loading docs locally

[snide]

@cchaos I checked into this. I'm worried this might be something due to the changes in our portal / focus trap stuff. It looks like there is an awful lot of extra empty divs wrapping the pop over that don't have a zindex assigned (the popover here has one of 0).

I don't think this is related to this PR, but it's likely something @thompsongl should take a look at.