Performance/CacheValueOverride: bug fix - false negative with fully qualified function call

The `isVariableAssignment()` method walks back from the function call to see if the result is being assigned, but did not take fully qualified function calls into account.

Fixed now.

Includes test.

Author: jrfnl

WordPressVIPMinimum/Sniffs/Performance/CacheValueOverrideSniff.php

@@ -83,9 +83,10 @@ public function process_matched_token( $stackPtr, $group_name, $matched_content
 	 */
 	private function isVariableAssignment( $stackPtr ) {
 
-		// Find the previous non-empty token.
+		// Find the previous non-empty token, but allow for FQN function calls.
 		$search   = Tokens::$emptyTokens;
 		$search[] = T_BITWISE_AND;
+		$search[] = T_NS_SEPARATOR;
 		$previous = $this->phpcsFile->findPrevious( $search, $stackPtr - 1, null, true );
 
 		if ( $this->tokens[ $previous ]['code'] !== T_EQUAL ) {

WordPressVIPMinimum/Tests/Performance/CacheValueOverrideUnitTest.1.inc

@@ -77,3 +77,8 @@ function functionCallsAreNotCaseSensitiveBad() {
 	do_something_else();
 	$cache_retrieved = false; // Bad.
 }
+
+function fqnFunctionCallBad() {
+	$shouldBeCaught = \wp_cache_get();
+	$shouldBeCaught = false; // Bad.
+}

WordPressVIPMinimum/Tests/Performance/CacheValueOverrideUnitTest.php

@@ -30,6 +30,7 @@ public function getErrorList( $testFile = '' ) {
 				return [
 					68 => 1,
 					78 => 1,
+					83 => 1,
 				];
 
 			default: