build: enable bundle_dts for forms package (#28854)

This PR also changes the name of NgNoValidate` to `ɵNgNoValidate`. This is because `ngcc` requires the node to retain the original name while dts bundler will rename the node is it's only exported using the aliases.

Example typings files:
```ts
declare class NgNoValidate{
}
export {NgNoValidateas ɵNgNoValidate}
```

will be emitted as
```ts
export declare class ɵNgNoValidate {
}
```

PR Close #28854

packages/forms/src/directives/ng_no_validate_directive.ts

@@ -29,5 +29,7 @@ import {Directive} from '@angular/core';
   selector: 'form:not([ngNoForm]):not([ngNativeValidate])',
   host: {'novalidate': ''},
 })
-export class NgNoValidate {
+export class ɵNgNoValidate {
 }
+
+export {ɵNgNoValidate as NgNoValidate};