New label: add color picker

What does this MR do and why?

Adds a color picker to the create label action.

Screenshots or screen recordings

New label dropdown

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New label page

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New issue

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How to set up and validate locally

1. Issuables: Go to an issue and create a new project label in the sidebar (e.g. http://gdk.test:3000/flightjs/Flight/-/issues/19)
2. MR: http://gdk.test:3000/flightjs/Flight/-/merge_requests/11
3. New label page: http://gdk.test:3000/flightjs/Flight/-/labels/new
4. New issue: http://gdk.test:3000/flightjs/Flight/-/issues/new

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #361846 (closed)