Add AVIF support

[adamsilverstein]

Trac ticket: https://core.trac.wordpress.org/ticket/51228

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[adamsilverstein]

@mukeshpanchal27 - note that it looks like tests broke in 49f4278 (#4612). those variables were used on the next line where the line return compact( 'width', 'height', 'type' ); uses a weird syntax to reference them.

Anyway, that function was poorly structured and had an inconsistent return structure; it already had a default return value set later in the function so I moved that up and return it when the mime type isn't avif in b492dbf (#4612)

[mukeshpanchal27]

Thanks, @adamsilverstein, for the update. I've left some nit-pick feedback and suggestions. Other than that, looks good to me.

[adamsilverstein]

Thanks, @adamsilverstein, for the update. I've left some nit-pick feedback and suggestions. Other than that, looks good to me.

Thanks for the careful review and suggestions, I have accepted your suggestions.

[github-actions]

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[github-actions]

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[adamsilverstein]

merged in https://core.trac.wordpress.org/changeset/57524