Change Use AI button to be more prominent

[vraja-pro]

Context

Summary

This PR can be summarized in the following changelog entry:

• Changes the AI generator button label and design.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Edit a post and:
  • Check the label of the AI generator button for Search appearance title is: Generate SEO title.
  • Check the label of the AI generator button for Search appearance description is: Generate meta description.
  • Check for Social appearance for facebook and x title AI generator button label is: Generate social title.
  • Check for Social appearance for facebook and x description AI generator button label is: Generate social description.
• Check the colors and border of the button match the design.
• Click on the button and check the spinner appears in the button.

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes https://github.com/Yoast/reserved-tasks/issues/713

[coveralls]

Pull Request Test Coverage Report for Build 0cfbb33fff80e2093829f657a0e073cdd2ad5fbd

Details

• 0 of 10 (0.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 52.89%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/js/src/ai-generator/components/app.js	0	10	0.0%

Files with Coverage Reduction	New Missed Lines	%
packages/js/src/ai-generator/components/app.js	1	2.21%

Totals
Change from base Build 81d2b4dba47f1f36d53a30afb3079916e29c1e30:	-0.02%
Covered Lines:	31233
Relevant Lines:	59725

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💛 - Coveralls

[thijsoo]

CR + ACC 👍