Adds lab icon and updates beta badge style

[ryankeairns]

Fixes #1280

Summary

In response to feedback and discussion around the current beta badge (see links in issue above), we're updating the EuiBetaBadge design to be more subtle, visually. Additionally, this PR adds a lab icon that can be used for icon-only beta badges.

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

[snide]

cc @tbragin and @skearns64. We'll get this into 6.5

[snide]

Looks good.

[cchaos]

Since there is a rush to get this in, I'm good with the changes (minus the icon naming tweak).

The new badge style looks great on the cards, but it falls a little in the keypad menu item version. But we can tackle that later.

[ryankeairns]

retest

[ryankeairns]

jenkins, test this