[PHPUnit120] Add BareVarToStubIntersectionRector

[TomasVotruba]

Similar to #689 (MockObjectVarToStubRector), adds a complementary rule.

When a property is converted to a Stub native type but its @var docblock holds only the bare mocked-class type, this rule adds the &Stub intersection.

 /**
- * @var FormBuilderInterface
+ * @var FormBuilderInterface&Stub
  */
 private \PHPUnit\Framework\MockObject\Stub $formBuilder;

Scope:

• only inside PHPUnit TestCase
• only properties already typed as native Stub
• only a bare single-class @var (skips union/intersection, and Stub/MockObject short names)

Registered in PHPUNIT_MOCK_TO_STUB and PHPUNIT_CODE_QUALITY sets. Complements MockObjectVarToStubRector, which deliberately skips this bare-var case.