Allow simple form of valid test case in ruletester (#32559)

types/eslint/eslint-tests.ts

@@ -539,4 +539,12 @@ ruleTester.run('my-rule', rule, {
     ]
 });
 
+ruleTester.run('simple-valid-test', rule, {
+    valid: [
+        'foo',
+        'bar',
+        { code: 'foo', options: [{ allowFoo: true }] },
+    ]
+});
+
 //#endregion

types/eslint/index.d.ts

@@ -540,7 +540,7 @@ export class RuleTester {
         name: string,
         rule: Rule.RuleModule,
         tests: {
-            valid?: RuleTester.ValidTestCase[];
+            valid?: Array<string | RuleTester.ValidTestCase>;
             invalid?: RuleTester.InvalidTestCase[];
         },
     ): void;