SDKv2 - Providers must only be specified either at the TestCase or TestStep level

### Module version
```
github.com/hashicorp/terraform-plugin-docs v0.19.4
github.com/hashicorp/terraform-plugin-framework v1.13.0
github.com/hashicorp/terraform-plugin-go v0.25.0
github.com/hashicorp/terraform-plugin-log v0.9.0
github.com/hashicorp/terraform-plugin-testing v1.10.0
github.com/ohler55/ojg v1.25.0
github.com/stretchr/testify v1.8.3
```

### Relevant provider source code

```go
var (
/*
Is this factory is barely used to create the block "terraform.required_providers" in the Terraform configuration??? It doesn't need for anything else?
*/
testAccProtoV6ProviderFactories = map[string]func() (tfprotov6.ProviderServer, error){
"http": providerserver.NewProtocol6WithError(New("test")()),
}
)

func TestHTTPProvider(t *testing.T) {
t.Parallel()

t.Run("should return an error when the URL is empty", func(t *testing.T) {
resource.UnitTest(t, resource.TestCase{
PreCheck: func() { testAccPreCheck(t) },
ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
Steps: []resource.TestStep{
{
ConfigDirectory: config.TestNameDirectory(),
ExpectError: regexp.MustCompile("Get \"posts/1\": unsupported protocol scheme \"\""),
},
},
})
})
...
```

### Terraform Configuration Files
File `internal/provider/testdata/TestHTTPProvider/should_return_an_error_when_the_URL_is_empty/main.tf`
```hcl
resource "http_request" "test1" {
method = "GET"
path = "/posts/1"
}
```

### Debug Output
```
=== RUN TestHTTPProvider
=== PAUSE TestHTTPProvider
=== CONT TestHTTPProvider
=== RUN TestHTTPProvider/should_return_an_error_when_the_URL_is_empty
provider_test.go:47: Test validation error: TestStep 1/1 validation error: Providers must only be specified either at the TestCase or TestStep level
--- FAIL: TestHTTPProvider/should_return_an_error_when_the_URL_is_empty (13.88s)

--- FAIL: TestHTTPProvider (13.89s)

FAIL

Debugger finished with the exit code 0
```

### Expected Behavior
The factory should be creating the provider's block, according to the Framework SDK? I'm the developer of this provider, and on the internet, there's no example. Even in the HashiCorp docs, even in the HashiCups project, and don't even in the Scaffolding. So, I'm not sure if I'm doing it rightly, but it's very inconsistent behavior. The final behavior should be creating the provider automatically trying to apply the resource and giving me the error of missing URL. Interesting that, if I use just `Config` parameter, I can bypass this "check".

### Actual Behavior
It just trigger the error presented. And if I remove the provider factory, it'll give another error.

### Steps to Reproduce
Just run the tests, any tests with the examples online using the structure I suggested. Doesn't matter to be honest, if you use the `ConfigDirectory` parameter, you are not going to be able to run the tests. You have to have another kind of provider factory which I don't know what is that.

### References
* https://github.com/hashicorp/terraform-provider-scaffolding-framework/blob/main/internal/provider/provider_test.go#L18
* https://github.com/rios0rios0/terraform-provider-http/blob/main/internal/provider/provider_test.go#L51
* https://developer.hashicorp.com/terraform/plugin/framework/acctests#protocol-version-6
* https://developer.hashicorp.com/terraform/plugin/sdkv2/testing/acceptance-tests
* https://developer.hashicorp.com/terraform/plugin/sdkv2