Switch to sirbrillig/phpcs-variable-analysis

Introduces a new dependency of `sirbrillig/phpcs-variable-analysis` which is a more maintained version of the existing `VariableAnalysis` sniff in VIPCS.

The new sniff is added to the `WordPressVIPMinimum` ruleset. `WordPress-VIP-Go` ruleset inherits this, and maintains its dropping of the severity for `UnusedVariable` and `UndefinedVariable` violations.

The ruleset tests have set the previously undefined variables (or changed some variable names), so that violations on each line are still specific to the thing being tested, and doesn't include extra violations due to the use of throwaway variables.

One of the reasons for changing was the previously false positive with respect to the use of `$this` inside closures inside class methods. A ruleset test has been added to cover this, and it correctly does not get flagged in the ruleset test.

The old `VariableAnalysis` has been marked as deprecated, until it can be removed in the next major release of VIPCS. This will stop any breakage of setups which reference `WordPressVIPMinimum.Variables.VariableAnalysis` in a custom ruleset. If called, it throws a warning, and then passes control to the new VariableAnalysis sniff. The deprecation notice is excluded if the sniff is not explicitly included, and the duplicate violation messages are also silenced.

The previously used `VariableAnalaysisHelper.php` has been removed completely, as no-one should have been referencing that directly.

Fixes #449.

WordPress-VIP-Go/ruleset-test.inc

@@ -1,5 +1,5 @@
 <?php
-
+$file = ''; $fp = ''; $dir = ''; $test = ''; $bar = ''; $array = []; $query_args = []; $url = ''; $query = ''; $page_title = ''; $true = true; $some_nasty_var = ''; $data = ''; $group = ''; $testing = ''; $this = new stdClass(); $needle = ''; $some_var = ''; $blogid = 1; $text = ''; $category_id = 123; $foo = ''; $bar = ''; $var = ''; $wp_rewrite = ''; $count = 1; $loop = 1; $a = ''; $b = ''; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- All set for VariableAnalysis checks.
 // WordPressVIPMinimum.Functions.RestrictedFunctions.file_ops_delete
 delete( $file ); // Warning + Message.
 
@@ -188,7 +188,7 @@ $wpdb = 'test'; // Error.
 $GLOBALS['domain']['subkey'] = 'something else'; // Error.
 
 // WordPress.WP.EnqueuedResources.NonEnqueuedScript
-echo wp_kses( '<script src="' . esc_url( $script ) . '">', [ 'script' => [ 'src' => [], ], ] ); // Warning + Message.
+echo wp_kses( '<script src="' . esc_url( $url ) . '">', [ 'script' => [ 'src' => [], ], ] ); // Warning + Message.
 ?> <script src="http://someurl/somefile.js"></script> <!-- Warning + Message. -->
 
 <!-- WordPress.WP.EnqueuedResources.NonEnqueuedStylesheet -->
@@ -207,12 +207,12 @@ require_once "my_file.php"; // Warning.
 require '../../my_file.php'; // Warning.
 include("http://www.google.com/bad_file.php"); // Warning.
 
-// WordPressVIPMinimum.Variables.VariableAnalysis.UndefinedVariable
+// VariableAnalysis.CodeAnalysis.VariableAnalysis.UndefinedVariable
 function foo_bar_bar() {
 	$b . 'test'; // Warning.
 }
 
-// WordPressVIPMinimum.Variables.VariableAnalysis.UnusedVariable
+// VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
 function foo_bar_foo() {
 	$a = 'Hello'; // Warning
 }
@@ -339,7 +339,7 @@ require_once __DIR__ . "/my_file.svg"; // Error.
 // WordPressVIPMinimum.Functions.CheckReturnValue
 $my_theme_options = get_option( 'my_theme', false );
 if ( array_key_exists( 'key', $my_theme_options ) ) { } // Error.
-echo '<a href="' . esc_url( get_term_link( $link ) ) . '">My term link</a>'; // Error.
+echo '<a href="' . esc_url( get_term_link( $var ) ) . '">My term link</a>'; // Error.
 
 // WordPressVIPMinimum.Functions.DynamicCalls
 $my_notokay_func = 'extract';
@@ -349,7 +349,7 @@ $my_notokay_func(); // Error.
 wp_cache_get_multi(); // Error.
 opcache_reset(); // Error.
 opcache_invalidate( 'test_script.php' ); // Error.
-opcache_compile_file( $test_script ); // Error.
+opcache_compile_file( $var ); // Error.
 opcache_​is_​script_​cached( 'test_script.php' ); // Error.
 opcache_​get_​status(); // Error.
 opcache_​get_​configuration(); // Error.
@@ -425,7 +425,7 @@ wpcom_vip_get_term_by(); // Warning.
 wpcom_vip_get_category_by_slug(); // Warning.
 
 // WordPressVIPMinimum.Functions.StripTagsSniff
-strip_tags( 'Test', $html ); // Warning.
+strip_tags( 'Test', $text ); // Warning.
 
 // WordPressVIPMinimum.Hooks.AlwaysReturnInFilter
 function bad_example_function_thing() { // Error.

WordPress-VIP-Go/ruleset-test.php

@@ -222,6 +222,7 @@
 		417 => 1,
 		418 => 1,
 		419 => 1,
+		420 => 2,
 		421 => 1,
 		423 => 1,
 		424 => 1,

WordPress-VIP-Go/ruleset.xml

@@ -244,10 +244,10 @@
 		<type>warning</type>
 		<severity>3</severity>
 	</rule>
-	<rule ref="WordPressVIPMinimum.Variables.VariableAnalysis.UndefinedVariable">
+	<rule ref="VariableAnalysis.CodeAnalysis.VariableAnalysis.UndefinedVariable">
 		<severity>3</severity>
 	</rule>
-	<rule ref="WordPressVIPMinimum.Variables.VariableAnalysis.UnusedVariable">
+	<rule ref="VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable">
 		<severity>1</severity>
 	</rule>
 	<rule ref="WordPressVIPMinimum.UserExperience.AdminBarRemoval">