CS: remove unnecessary ignore annotations [2]

It is perfectly possible to write a commented regex with layout for readability by using the `x` modifier.

As per the manual:
>  x (PCRE_EXTENDED)
>     If this modifier is set, whitespace data characters in the pattern are totally ignored except when escaped or inside a character class, and characters between an unescaped # outside a character class and the next newline character, inclusive, are also ignored. This is equivalent to Perl's /x modifier, and makes it possible to include commentary inside complicated patterns.
>     Note, however, that this applies only to data characters. Whitespace characters may never appear within special character sequences in a pattern, for example within the sequence (?( which introduces a conditional subpattern.

Ref: https://www.php.net/manual/en/reference.pcre.pattern.modifiers.php

This commit rewrites these two regexes to use the `x` modifier and gets rid of the unnecessary `phpcs:disable` comments.

The tests in the `tests/phpunit/tests/db/dbDelta.php` file cover this change.

src/wp-admin/includes/upgrade.php

@@ -2910,31 +2910,29 @@ function dbDelta( $queries = '', $execute = true ) { // phpcs:ignore WordPress.N
 					 */
 
 					// Extract type, name and columns from the definition.
-					// phpcs:disable Squiz.Strings.ConcatenationSpacing.PaddingFound -- don't remove regex indentation
 					preg_match(
-						'/^'
-						.   '(?P<index_type>'             // 1) Type of the index.
-						.       'PRIMARY\s+KEY|(?:UNIQUE|FULLTEXT|SPATIAL)\s+(?:KEY|INDEX)|KEY|INDEX'
-						.   ')'
-						.   '\s+'                         // Followed by at least one white space character.
-						.   '(?:'                         // Name of the index. Optional if type is PRIMARY KEY.
-						.       '`?'                      // Name can be escaped with a backtick.
-						.           '(?P<index_name>'     // 2) Name of the index.
-						.               '(?:[0-9a-zA-Z$_-]|[\xC2-\xDF][\x80-\xBF])+'
-						.           ')'
-						.       '`?'                      // Name can be escaped with a backtick.
-						.       '\s+'                     // Followed by at least one white space character.
-						.   ')*'
-						.   '\('                          // Opening bracket for the columns.
-						.       '(?P<index_columns>'
-						.           '.+?'                 // 3) Column names, index prefixes, and orders.
-						.       ')'
-						.   '\)'                          // Closing bracket for the columns.
-						. '$/im',
+						'/^
+							(?P<index_type>             # 1) Type of the index.
+								PRIMARY\s+KEY|(?:UNIQUE|FULLTEXT|SPATIAL)\s+(?:KEY|INDEX)|KEY|INDEX
+							)
+							\s+                         # Followed by at least one white space character.
+							(?:                         # Name of the index. Optional if type is PRIMARY KEY.
+								`?                      # Name can be escaped with a backtick.
+									(?P<index_name>     # 2) Name of the index.
+										(?:[0-9a-zA-Z$_-]|[\xC2-\xDF][\x80-\xBF])+
+									)
+								`?                      # Name can be escaped with a backtick.
+								\s+                     # Followed by at least one white space character.
+							)*
+							\(                          # Opening bracket for the columns.
+								(?P<index_columns>
+									.+?                 # 3) Column names, index prefixes, and orders.
+								)
+							\)                          # Closing bracket for the columns.
+						$/imx',
 						$fld,
 						$index_matches
 					);
-					// phpcs:enable
 
 					// Uppercase the index type and normalize space characters.
 					$index_type = strtoupper( preg_replace( '/\s+/', ' ', trim( $index_matches['index_type'] ) ) );
@@ -2952,29 +2950,27 @@ function dbDelta( $queries = '', $execute = true ) { // phpcs:ignore WordPress.N
 					// Normalize columns.
 					foreach ( $index_columns as $id => &$index_column ) {
 						// Extract column name and number of indexed characters (sub_part).
-						// phpcs:disable Squiz.Strings.ConcatenationSpacing.PaddingFound -- don't remove regex indentation
 						preg_match(
-							'/'
-							.   '`?'                      // Name can be escaped with a backtick.
-							.       '(?P<column_name>'    // 1) Name of the column.
-							.           '(?:[0-9a-zA-Z$_-]|[\xC2-\xDF][\x80-\xBF])+'
-							.       ')'
-							.   '`?'                      // Name can be escaped with a backtick.
-							.   '(?:'                     // Optional sub part.
-							.       '\s*'                 // Optional white space character between name and opening bracket.
-							.       '\('                  // Opening bracket for the sub part.
-							.           '\s*'             // Optional white space character after opening bracket.
-							.           '(?P<sub_part>'
-							.               '\d+'         // 2) Number of indexed characters.
-							.           ')'
-							.           '\s*'             // Optional white space character before closing bracket.
-							.       '\)'                  // Closing bracket for the sub part.
-							.   ')?'
-							. '/',
+							'/
+								`?                      # Name can be escaped with a backtick.
+									(?P<column_name>    # 1) Name of the column.
+										(?:[0-9a-zA-Z$_-]|[\xC2-\xDF][\x80-\xBF])+
+									)
+								`?                      # Name can be escaped with a backtick.
+								(?:                     # Optional sub part.
+									\s*                 # Optional white space character between name and opening bracket.
+									\(                  # Opening bracket for the sub part.
+										\s*             # Optional white space character after opening bracket.
+										(?P<sub_part>
+											\d+         # 2) Number of indexed characters.
+										)
+										\s*             # Optional white space character before closing bracket.
+									\)                  # Closing bracket for the sub part.
+								)?
+							/x',
 							$index_column,
 							$index_column_matches
 						);
-						// phpcs:enable
 
 						// Escape the column name with backticks.
 						$index_column = '`' . $index_column_matches['column_name'] . '`';