Convert EuiExpression to TS

[cchaos]

No more EuiExpressionButton

The breaking change on this is that there were 2 components EuiExpression and EuiExpressionButton. EuiExpression did absolutely nothing but be a div wrapper. So I removed the EuiExpressionButton as the name was limiting and just made it EuiExpression.

More options

I also added more options to the EuiExpression:

• color: for specifying the color of the description (defaults to 'success')
• uppercase: for telling the component to or not to uppercase the description (defaults to true)
• onClick: now this option forces the component to be a button with some styles associated with click-ability otherwise if a function is not provided it will be a "ready only" style.

I also changed the font family to our mono spaced font, and reduced some of the height for a more compressed look.

cc @nreese

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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]

Minor design questions, that I'm fine with either way. Looks a lot better.