MU WPCOM: Port enqueue_coblocks_gallery_scripts from the ETK

[arthur791004]

Related to https://github.com/Automattic/dotcom-forge/issues/8208

Proposed changes:

• Port enqueue_coblocks_gallery_scripts from the ETK. I'm unsure whether it's still in use (the feature requires the specific blocks in the header/footer of the legacy fse) so just moving the code from ETK to jetpack-mu-wpcom to avoid missing something

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?
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Jetpack product discussion

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

Testing instructions:

• Apply changes to your site
• Just make sure nothing broken

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the mu-wpcom/coblocks branch.

  • For jetpack-mu-wpcom changes, also add define( 'JETPACK_MU_WPCOM_LOAD_VIA_BETA_PLUGIN', true ); to your wp-config.php file.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack-mu-wpcom-plugin mu-wpcom/coblocks
  

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[github-actions]

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[taipeicoder]

Smoke-tested and LGTM, there are some Phan errors though.

The base branch was changed.