Allow users to validate Chocolatey sources directly

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### Checklist

- [x] I have verified this is the correct repository for opening this issue.
- [x] I have verified no other issues exist related to my request.

### Is Your Feature Request Related To A Problem? Please describe.

In this [issue comment](https://github.com/chocolatey/choco/issues/3506#issuecomment-2585163508) the user would have benefitted from Chocolatey CLI being able to validate the configured sources.

### Describe The Solution. Why is it needed?

Adding a command such as `choco source validate` (naming is hard) to allow all, or a specific source (perhaps using `choco source validate --source `) to be "checked" to ensure Chocolatey CLI can use it.

What "checked" means we would need to define. But it could be as simple as retrieving a package list, or:

* Check if it's reachable. Is the URL correct?
* What type of source is it: v2 oData, v3 JSON, local folder / shared drive, etc.
* If authentication is provided, can we authenticate?
* Does it have a search endpoint?

### Additional Context

_No response_

### Related Issues

- [Issue comment where the idea came from](https://github.com/chocolatey/choco/issues/3506#issuecomment-2585163508).

No files or tests are named. Start by reviewing the existing `choco source` commands and the context in issue #3506's linked comment, then define which source checks and command options are in scope; the work is done when the validation behavior and its expected outcomes are specified and covered by appropriate tests.

Written by the indexing model from the issue text.