Some EuiSuperSelect fixes

[cchaos]

• Fixed size of context menu when there’s no initial selection
• Don’t use underlines for focus states, but background colors instead - It's possible to have blocks of text as options which looks odd to underline a whole paragraph

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To test:

Change this state to null:

eui/src-docs/src/views/super_select/super_select.js

Line 33 in f7fbd94

value: this.options[1].value,

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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

[chandlerprall]

jenkins test this

[chandlerprall]

code changes LGTM