Add /recommendations/evaluation endpoint handling

[robertsreberski]

Proposed changes:

• Adds recommendation evaluation endpoint handling and saving it as Jetpack option.
• Improves useWelcomeBanner() hook
• Improves useSimpleMutation() hook cc @CodeyGuyDylan

Other information:

• [ ] Have you written new tests for your changes, if applicable?
• [ ] Have you checked the E2E test CI results, and verified that your changes do not break them?
• [ ] Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

This PR requires you to point Jetpack to your sandbox with D153037-code patched

• Create JN site (with “Enable Sandbox Access” option enabled)

• Set Jetpack constant JETPACK__SANDBOX_DOMAIN to your sandbox

• Install Jetpack through Jetpack Beta plugin, with add/recommendations-evaluation-endpoint feature branch

• Go to /wp-admin/admin.php?page=my-jetpack and connect your site, evaluation form will be displayed

• Open Network tab in Web Inspector

• Select some options and click "See solutions"

• Make sure that /evaluation and /save-evaluation endpoints returned successful responses

• Welcome Flow banner should disappear after evaluation is saved ✨