Handle empty comments in AJAX batches

[ArkaPrabhaChowdhury]

Trac ticket: https://core.trac.wordpress.org/ticket/39418

This changes the Comments screen Empty Spam/Empty Trash action to use AJAX batches when JavaScript is available, while keeping the existing form submit path as the no-JS fallback.

Validation:

• php vendor/bin/phpcbf --standard=phpcs.xml.dist src/wp-admin/admin-ajax.php src/wp-admin/includes/ajax-actions.php tests/phpunit/tests/ajax/wpAjaxDeleteComment.php
• php vendor/bin/phpcs --standard=phpcs.xml.dist src/wp-admin/admin-ajax.php src/wp-admin/includes/ajax-actions.php tests/phpunit/tests/ajax/wpAjaxDeleteComment.php
• npx grunt jshint:core --file=src/js/_enqueues/admin/edit-comments.js
• npm run test:php -- --group ajax tests/phpunit/tests/ajax/wpAjaxDeleteComment.php

[github-actions]

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