Add labels for permalink settings error textareas

[sabernhardt]

When saving permalinks, if the server configuration file or the root directory is unwritable, the error message contains a read-only textarea without a label tag.

[sabernhardt]

53142.diff​ uses the same "Rewrite rules:" label text for the single textarea, whether it's for the web.config or .htaccess file.

I also added two rows to the .htaccess rules textarea.

[sabernhardt]

current permalink messages without the label

[sabernhardt]

adding a label to each error message's rewrite rules textarea (and adding rows to htaccess textarea)

[sabernhardt]

Testing process

1. Ideally, make the web.config file, root directory or .htaccess file unwritable. If that's not possible in your installation, adjust conditions within options-permalink.php to return true to force each error (see below).
2. Navigate to Settings -> Permalinks.
3. Select a different permalink option and Save changes.
4. Check for a label with the read-only form element.

Ways to fake each situation

web.config is not writable

Replace the 3 consecutive conditional statements with true statements:

	if ( $iis7_permalinks ) :
		if ( isset( $_POST['submit'] ) && $permalink_structure && ! $using_index_permalinks && ! $writable ) :
			if ( file_exists( $home_path . 'web.config' ) ) :

root directory is not writable to edit/create web.config

Replace only the first 2 conditions with true statements (file_exists( $home_path . 'web.config' ) needs to remain false):

	if ( $iis7_permalinks ) :
		if ( isset( $_POST['submit'] ) && $permalink_structure && ! $using_index_permalinks && ! $writable ) :

.htaccess is not writable

Only replace this statement with a true condition:

	if ( $permalink_structure && ! $using_index_permalinks && ! $writable && $htaccess_update_required ) :

[joedolson]

In 50830:

Permalinks: Add labels for permalink configuration fields.

If the current server configuration doesn't allow WordPress to edit permalink settings, the textarea with new rules to use was not labeled. Add labels and aria-describedby pointing to the field description.

Props sabernhardt
Fixes #53142.