RequestDelegate is not injected on middlewares using Primary Constructor

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the bug

When using primary constructors, the `RequestDelegate` comes null, causing `404` to be returned everytime. When using default constructors, it is injected just fine, which is expected.


### Expected Behavior

Since primary constructor is the same of having a single construtor definition, it should have the same behaviour as injecting the `RequestDelegate` in the default constructor.

### Steps To Reproduce

• Create a middleware
• Use the new primary constructor to inject the RequestDelegate
• Verify during debug that it is injected as null

### Exceptions (if any)

_No response_

### .NET Version

8

### Anything else?

_No response_

Start by reproducing the middleware behavior described in issue #53490 on .NET 8, comparing a primary constructor with a default constructor. Trace how RequestDelegate is supplied during middleware activation and confirm the fix by verifying it is non-null and the middleware no longer returns an unintended 404.

Written by the indexing model from the issue text.