refactor(UseLeadingBackslash): Replace sniff with upstream version from Slevomat (#3554461)

Author: klausi

.github/workflows/testing.yml

@@ -87,6 +87,7 @@ jobs:
           sed -i 's/Drupal.Classes.UnusedUseStatement/SlevomatCodingStandard.Namespaces.UnusedUses/g' phpcs.xml.dist
           sed -i '/<rule ref="SlevomatCodingStandard.Exceptions.RequireNonCapturingCatch" \/>/a \  <rule ref="SlevomatCodingStandard.Namespaces.UseFromSameNamespace"/>' phpcs.xml.dist
           sed -i 's@<rule ref="Drupal.Classes.ClassFileName"/>@<rule ref="Squiz.Classes.ClassFileName">\n    <!-- Disable class name to file name matching for *Test.php files. -->\n    <exclude-pattern>*/tests/*/*(Test|TestBase).php</exclude-pattern>\n  </rule>@' phpcs.xml.dist
+          sed -i 's/Drupal.Classes.UseLeadingBackslash/SlevomatCodingStandard.Namespaces.UseDoesNotStartWithBackslash/g' phpcs.xml.dist
           find . -type f -name "*.php" -exec sed -i 's#// phpcs:ignore Drupal.Classes.PropertyDeclaration, Drupal.NamingConventions.ValidVariableName.LowerCamelName, Drupal.Commenting.VariableComment.Missing#// phpcs:ignore Drupal.NamingConventions.ValidVariableName.LowerCamelName,PSR2.Classes.PropertyDeclaration.Underscore#g' {} +
           find . -type f -name "*.php" -exec sed -i 's#// @codingStandardsIgnoreLine#// phpcs:ignore#g' {} +
           find . -type f -name "*.php" -exec sed -i 's#// @codingStandardsIgnoreFile#// phpcs:ignoreFile#g' {} +

coder_sniffer/Drupal/Sniffs/Classes/UseLeadingBackslashSniff.php

@@ -136,6 +136,7 @@
   <rule ref="SlevomatCodingStandard.ControlStructures.NewWithParentheses"/>
   <rule ref="SlevomatCodingStandard.ControlStructures.RequireNullCoalesceOperator"/>
   <rule ref="SlevomatCodingStandard.Namespaces.UnusedUses"/>
+  <rule ref="SlevomatCodingStandard.Namespaces.UseDoesNotStartWithBackslash"/>
   <rule ref="SlevomatCodingStandard.Namespaces.UseFromSameNamespace"/>
   <rule ref="SlevomatCodingStandard.PHP.ShortList"/>
   <rule ref="SlevomatCodingStandard.TypeHints.DeclareStrictTypes">

coder_sniffer/Drupal/ruleset.xml

@@ -404,6 +404,10 @@ protected function getErrorList(string $testFile): array
                 85 => 1,
                 98 => 1,
             ];
+        case 'UseLeadingBackslashUnitTest.inc':
+            return [
+                8  => 1,
+            ];
         case 'WrongClassName.php':
             return [
                 6 => 1,