Add site setting to hide the Action Bar

[ntsekouras]

Related to #53830

This PR adds a new general setting (wpcom_show_action_bar) to conditionally show the Action Bar on the front end of a site. The goal is to have a truthy default value to preserve the current behavior that Action Bar is shown.

The main issue will need two more PRs to be complete that I'll create and link shortly:

1. wpcom to check this option and not enqueue the Action Bar
2. Jetpack to add UI for this setting in classic wp-admin interface Action Bar: Add Action Bar visibility general setting jetpack#41015

Notes

1. I need a bit help about how settings are registered in calypso. I tried looking at other settings but there are many places that some options used and I haven't fully understood the proper place to add/save the option.
2. Some other options are being tracked. Should it be the case for this one too?
3. What would be the suggested way to handle an option that is kind of boolean but wp-admin stores the 1 number value to indicate it's set.

Testing Instructions

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 UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• 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]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129718

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129718&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129718&env=a8c-for-agencies

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications

To test WordPress.com changes, run install-plugin.sh $pluginSlug add/show-action-bar-setting-ui on your sandbox.

[matticbot]

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

App Entrypoints (~10 bytes added 📈 [gzipped])

name                 parsed_size           gzip_size
entry-subscriptions        +22 B  (+0.0%)      +10 B  (+0.0%)
entry-stepper              +22 B  (+0.0%)      +10 B  (+0.0%)
entry-main                 +22 B  (+0.0%)      +10 B  (+0.0%)
entry-login                +22 B  (+0.0%)      +10 B  (+0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Sections (~217 bytes added 📈 [gzipped])

name           parsed_size           gzip_size
settings            +655 B  (+0.1%)     +199 B  (+0.1%)
site-settings        +70 B  (+0.0%)      +18 B  (+0.0%)

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.