Add theme_color_override_with_admin_color_scheme flag and use to update meta theme color tag

[ciampo]

Related to #98335

Needs #98380 to be merged first

Proposed Changes

• Add a new theme_color_override_with_admin_color_scheme environment config option
• Use it to enable/disable updating the <meta name="theme-color" /> tag dynamically on the client whenever a user updates the admin color scheme

Why are these changes being made?

To match the desired behavior described in #98335. This feature is currently broken, as the data-colorscheme attribute that the logic relies is not applied in the code anymore (probably removed my mistake in a previous refactor).

This PR reinstates the behavior, but it changes the logic: instead of relying on the theme-color being defined or not (which is fragile and unclear), it uses a dedicated environment config option. Not only this logic is more clear, but it is also compatible with the changes being proposed in #98380

Testing Instructions

• Load calypso in any wordpress.com environments
• Observe the initial value of the <meta name="theme-color" /> tag in the page
• Change the admin color scheme (by visiting /wp-admin/profile.php)
• Verify that the interface changes color dynamically as a color scheme is chosen
• Save the user preferences and go back to calypso UI
• Observe the new value of the <meta name="theme-color" /> tag and make sure it follows the main color of the new chosen theme
• Change the theme_color_override_with_admin_color_scheme to false for the relevant environment (eg development), and make sure that the <meta name="theme-color" /> tag doesn't follow the admin color scheme
• A4A and jetpack cloud environments should also keep the value of the <meta name="theme-color" /> tag fixed, ie. they should not update it to follow any changes from the admin color scheme.

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-129892

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129892&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-129892&env=a8c-for-agencies

[matticbot]

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

App Entrypoints (~2 bytes added 📈 [gzipped])

name         parsed_size           gzip_size
entry-main         +67 B  (+0.0%)       +2 B  (+0.0%)
entry-login        +67 B  (+0.0%)       +2 B  (+0.0%)

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

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.

[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 fix/theme_color_update_admin_color_scheme_config_option on your sandbox.

[ciampo]

@tyxla also pointed out another environment config variable called me/account/color-scheme-picker which is potentially used to enable/disable color schemes although I don't have much context around it — @fushar @okmttdhr it looks like you may have more context on this, given the work on the "site level user profile". Could you advise? Thank you 🙏