Fix EuiFilterGroupButton bolding with notification and...

[cchaos]

Two things ended up getting fixed with this one

1. I realized that when sending textProps and contentProps to EuiButton and EuiButtonEmpty, I wasn't accounting for the fact that it would replace className is passed down.

So these components now append the button classNames to any classNames passed in those objects before applying those props objects to the element.

2. The bolding trick now works on EuiFilterGroupButtons that have the numFilters notification

Before

After

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]

Found the same issue on EuiBadge and fixed that as well.

[chandlerprall]

changes LGTM