refactor(core): declare TestModuleMetadata as an interface (#45891)

This allows the documentation for the options `errorOnUnknownElements` and `errorOnUnknownProperties` to be displayed in the docs.
They aren't currently displayed, as `TestModuleMetadata` is a type and not an interface.
See https://next.angular.io/api/core/testing/TestModuleMetadata

PR Close #45891

goldens/public-api/core/testing/index.md

@@ -221,15 +221,20 @@ export interface TestEnvironmentOptions {
 }
 
 // @public (undocumented)
-export type TestModuleMetadata = {
-    providers?: any[];
+export interface TestModuleMetadata {
+    // (undocumented)
     declarations?: any[];
+    errorOnUnknownElements?: boolean;
+    errorOnUnknownProperties?: boolean;
+    // (undocumented)
     imports?: any[];
+    // (undocumented)
+    providers?: any[];
+    // (undocumented)
     schemas?: Array<SchemaMetadata | any[]>;
+    // (undocumented)
     teardown?: ModuleTeardownOptions;
-    errorOnUnknownElements?: boolean;
-    errorOnUnknownProperties?: boolean;
-};
+}
 
 // @public
 export function tick(millis?: number, tickOptions?: {

packages/core/testing/src/test_bed_common.ts

@@ -45,11 +45,11 @@ export const ComponentFixtureNoNgZone = new InjectionToken<boolean[]>('Component
 /**
  * @publicApi
  */
-export type TestModuleMetadata = {
-  providers?: any[],
-  declarations?: any[],
-  imports?: any[],
-  schemas?: Array<SchemaMetadata|any[]>,
+export interface TestModuleMetadata {
+  providers?: any[];
+  declarations?: any[];
+  imports?: any[];
+  schemas?: Array<SchemaMetadata|any[]>;
   teardown?: ModuleTeardownOptions;
   /**
    * Whether NG0304 runtime errors should be thrown when unknown elements are present in component's
@@ -65,7 +65,7 @@ export type TestModuleMetadata = {
    * @see https://angular.io/errors/NG8002 for the description of the error and how to fix it
    */
   errorOnUnknownProperties?: boolean;
-};
+}
 
 /**
  * @publicApi