Composer: update to WP Test Utils 1.0.0

[jrfnl]

Summary

This PR can be summarized in the following changelog entry:

• Updates dev tools

Relevant technical choices:

WP Test Utils 1.0.0 provides cross-version compatibility with the test setup from WP < 5.9 and WP 5.9+.

Includes updating the dependencies of WP Test Utils.

Refs:

• https://github.com/Yoast/wp-test-utils/releases/
• https://github.com/Yoast/PHPUnit-Polyfills/releases/
• https://github.com/mockery/mockery/releases/tag/1.3.5
• https://github.com/antecedent/patchwork/releases

Test instructions

This PR can be tested by following these steps:

• N/A If the build passes, we're good.