Add a dropdown for choosing MRVA result format

[shati-patel]

I've added a new component for picking the format for MRVA results:

It follows the style of the existing Sort and Filter dropdowns:

Note that I haven't hooked this new component up to the rest of the view yet, so it won't show up anywhere (except in Storybook). See internal linked issue for details!

Checklist

N/A—no user impact yet 🐘

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[charisk]

Looks great! Thanks for adding a story for it too!

[charisk]

I think we can use the enum values here too since they have the same text as we want.

Suggested change

	<VSCodeOption value={ResultFormat.Alerts}>Alerts</VSCodeOption>
	<VSCodeOption value={ResultFormat.Alerts}>{ResultFormat.Alerts}</VSCodeOption>

BTW, I don't remember using string enum values with spaces in them 🤔 I've looked in our repo and it doesn't look like we're following any kind of convention though (some are capital case, some lower case, some camel case, some pascal case, and in some rare occasions we have spaces 😓 ).

[shati-patel]

Thanks! And yeah, it looks like we're pretty inconsistent with enums 🙈