refactor: use explicit specifier for form field control harness re-export

Instead of using a star export, we should use an explicit specifier
for the `@angular/material/form-field/testing/control` re-export.

This satisfies Microsoft's API extractor which will complain as
it cannot resolve the entry-point. Within an API golden test, first-party
packages/entry-points are always considered external and therefore not resolvable.

Author: devversion

src/material-experimental/mdc-form-field/testing/public-api.ts

@@ -6,10 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-// Re-export everything from the "form-field/testing/control" entry-point. To avoid
-// circular dependencies, harnesses for default form-field controls (i.e. input, select)
+// Re-export the base control harness from the "form-field/testing/control" entry-point. To
+// avoid circular dependencies, harnesses for form-field controls (i.e. input, select)
 // need to import the base form-field control harness through a separate entry-point.
-export * from '@angular/material/form-field/testing/control';
+export {MatFormFieldControlHarness} from '@angular/material/form-field/testing/control';
 
 export {FormFieldHarnessFilters} from '@angular/material/form-field/testing';
 export * from './form-field-harness';

src/material/form-field/testing/public-api.ts

@@ -6,10 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-// Re-export everything from the "form-field/testing/control" entry-point. To avoid
-// circular dependencies, harnesses for default form-field controls (i.e. input, select)
+// Re-export the base control harness from the "form-field/testing/control" entry-point. To
+// avoid circular dependencies, harnesses for form-field controls (i.e. input, select)
 // need to import the base form-field control harness through a separate entry-point.
-export * from '@angular/material/form-field/testing/control';
+export {MatFormFieldControlHarness} from '@angular/material/form-field/testing/control';
 
 export * from './form-field-harness';
 export * from './form-field-harness-filters';

tools/public_api_guard/material/form-field-testing.md

@@ -25,6 +25,8 @@ export interface FormFieldHarnessFilters extends BaseHarnessFilters {
     hasErrors?: boolean;
 }
 
+export { MatFormFieldControlHarness }
+
 // @public
 export class MatFormFieldHarness extends _MatFormFieldHarnessBase<FormFieldControlHarness> {
     // (undocumented)
@@ -94,9 +96,6 @@ export abstract class _MatFormFieldHarnessBase<ControlHarness extends MatFormFie
     protected abstract _suffixContainer: AsyncFactoryFn<TestElement | null>;
 }
 
-
-export * from "@angular/material/form-field/testing/control";
-
 // (No @packageDocumentation comment for this package)
 
 ```