Introduce has_content() helper function

[salmanshafiq8630]

Currently, there is no dedicated helper function for determining whether a post contains content.

Developers typically check the post_content property directly:

<?php
$post = get_post( $post );

if ( $post && '' !== trim( $post->post_content ) ) {
    // The post has content.
}

This proposal introduces a new has_content() helper function, similar to has_excerpt(), that provides a consistent API for checking whether a post contains non-empty content.

The function would:

• Accept a post ID, WP_Post object, or null.
• Return true if the post contains non-empty content after trimming whitespace.
• Return false if the post does not exist or its content is empty.

https://core.trac.wordpress.org/ticket/65511