chore(eslint): migrate from eslint-plugin-vitest to @vitest/eslint-plugin and run rules only on test files (#4014)

This PR makes three small changes to the ESLint setup:

1. Migrate from
[eslint-plugin-vitest](https://www.npmjs.com/package/eslint-plugin-vitest)
to it's successor
[@vitest/eslint-plugin](https://www.npmjs.com/package/@vitest/eslint-plugin).
2. Change the eslint config so that only the test files are checked with
the vitest rules. Previously, it was just unnecessary and inefficient to
check all js files with them.
3. We had defined some of the test rules as warnings, but that is not
really ideal. I changed them to errors.

Author: KristjanESPERANTO

eslint.config.mjs

@@ -6,7 +6,7 @@ import jsdocPlugin from "eslint-plugin-jsdoc";
 import packageJson from "eslint-plugin-package-json";
 import playwright from "eslint-plugin-playwright";
 import stylistic from "@stylistic/eslint-plugin";
-import vitest from "eslint-plugin-vitest";
+import vitest from "@vitest/eslint-plugin";
 
 export default defineConfig([
 	globalIgnores(["config/**", "modules/**/*", "!modules/default/**", "js/positions.js"]),
@@ -17,16 +17,15 @@ export default defineConfig([
 			globals: {
 				...globals.browser,
 				...globals.node,
-				...vitest.environments.env.globals,
 				Log: "readonly",
 				MM: "readonly",
 				Module: "readonly",
 				config: "readonly",
 				moment: "readonly"
 			}
 		},
-		plugins: {js, stylistic, vitest},
-		extends: [importX.recommended, vitest.configs.recommended, "js/recommended", jsdocPlugin.configs["flat/recommended"], "stylistic/all"],
+		plugins: {js, stylistic},
+		extends: [importX.recommended, "js/recommended", jsdocPlugin.configs["flat/recommended"], "stylistic/all"],
 		rules: {
 			"@stylistic/array-element-newline": ["error", "consistent"],
 			"@stylistic/arrow-parens": ["error", "always"],
@@ -59,23 +58,6 @@ export default defineConfig([
 			"import-x/newline-after-import": "error",
 			"import-x/order": "error",
 			"init-declarations": "off",
-			"vitest/consistent-test-it": "warn",
-			"vitest/expect-expect": [
-				"warn",
-				{
-					assertFunctionNames: [
-						"expect",
-						"testElementLength",
-						"testTextContain",
-						"doTest",
-						"runAnimationTest",
-						"waitForAnimationClass",
-						"assertNoAnimationWithin"
-					]
-				}
-			],
-			"vitest/prefer-to-be": "warn",
-			"vitest/prefer-to-have-length": "warn",
 			"max-lines-per-function": ["warn", 400],
 			"max-statements": "off",
 			"no-global-assign": "off",
@@ -135,6 +117,36 @@ export default defineConfig([
 			"sort-keys": "off"
 		}
 	},
+	{
+		files: ["tests/**/*.js"],
+		languageOptions: {
+			globals: {
+				...vitest.environments.env.globals
+			}
+		},
+		plugins: {vitest},
+		extends: [vitest.configs.recommended],
+		rules: {
+			"vitest/consistent-test-it": "error",
+			"vitest/expect-expect": [
+				"error",
+				{
+					assertFunctionNames: [
+						"expect",
+						"testElementLength",
+						"testTextContain",
+						"doTest",
+						"runAnimationTest",
+						"waitForAnimationClass",
+						"assertNoAnimationWithin"
+					]
+				}
+			],
+			"vitest/max-nested-describe": ["error", {max: 3}],
+			"vitest/prefer-to-be": "error",
+			"vitest/prefer-to-have-length": "error"
+		}
+	},
 	{
 		files: ["tests/configs/modules/weather/*.js"],
 		rules: {