Add a chip multi-select component

[nfmohit]

Feature Description

In order to facilitate the selection of post types where RRM CTAs should appear, a chip multi-select component should be added to Site Kit.

This component did exist previously in Site Kit as part of Thank with Google, but was then removed. It can largely be salvaged from Git history.

• See relevant section in the design doc.
• See Figma designs.

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Acceptance criteria

Implementation Brief

Test Coverage

QA Brief

Changelog entry