A4A: Implement Agency ownership transfer

[tiagonoronha]

Adds the possibility to transfer the Agency Owner role to a different team member on the agency account.

Related to https://github.com/Automattic/automattic-for-agencies-dev/issues/1128.

Proposed Changes

Testing Instructions

• Sandbox public-api.wordpress.com.
• Apply D166876-code.
• In your test agency, invite a user to the agency.
• Log in as the agency owner, navigate to Team, click on Actions for the user you invited, and select Transfer ownership.
• A confirmation modal should appear.
• Click the Transfer ownership button in the confirmation modal.
• Confirm that the table reloads and you are no longer listed as the agency owner.

Pre-merge Checklist

• [ ] Has the general commit checklist been followed? (PCYsg-hS-p2)
• [ ] Have you written new tests for your changes?
• [ ] Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• [ ] Have you checked for TypeScript, React or other console errors?
• [ ] Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• [ ] Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• [ ] For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions[bot]]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-8bae9311e2e258ca02b6cc0fff6445a0fdf7733a

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-8bae9311e2e258ca02b6cc0fff6445a0fdf7733a&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-8bae9311e2e258ca02b6cc0fff6445a0fdf7733a&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~183 bytes added 📈 [gzipped])

``` name parsed_size gzip_size a8c-for-agencies-team +1144 B (+0.1%) +183 B (+0.1%) ``` Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

**Parsed Size:** Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory. **Gzip Size:** Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[cleacos]

I've tested it partially (I have issues with my sandbox). I can select the Transfer ownership option and I see the confirm modal. The code looks good.