i18n: Fix localization of themes filters

[dlind1]

Part of I18N-223

Proposed Changes

• Fix the loading of theme filters on /themes page to use the correct translations.

Before:

After:

Why are these changes being made?

Currently there are several issues with loading the translated filters on /themes page:

• The filters are calculated once in the constructor of ThemeShowcase, which means that on the initial load the English filters from initialReduxState would always be used.
• Occasionally QueryThemeFilters is loading the filters before the locale has been set, which means that the filters are loaded using the English locale.
• Both of these mean that users with a non-English locale would use the theme filters in English on first visit to the /themes logged-in page.

Testing Instructions

To reproduce:

1. Switch to a popular non-English locale in Calypso (e.g. Spanish or German).
2. Go to https://wordpress.com/themes/{your site} in a fresh tab/window.
3. Confirm that the theme filters appear in English.
4. Navigate to another Calypso page, then back to to /themes and confirm that it's now translated. If it's still not translated, repeat this step.
5. Test on local Calypso instance or calypso.live and confirm that the issue is fixed. You can also check the network tab for calls to theme-filters to check that it's using the correct locale.
6. Check the logged-out themes showcase for regression testing.

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-145026

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-145026&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-145026&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

• help-center
• notifications
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug fix/themes-filters-loading on your sandbox.

[matticbot]

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

Sections (~56 bytes added 📈 [gzipped])

name    parsed_size           gzip_size
themes       +263 B  (+0.0%)      +52 B  (+0.0%)
theme        +127 B  (+0.0%)      +29 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.