Support `.bicepparam` files as the sole parameters without requiring `--file`

[Gijsreyn]

Summary of the new feature / enhancement

As a user, I would like to specify the .bicepparam file as the sole input to dsc.exe. For example, when using New-AzSubscriptionDeployment (or other commands), you can specify:

New-AzSubscriptionDeployment -TemplateParameterFile main.bicepparam

For dsc.exe, this is not the case and always requires --file.

Proposed technical implementation details (optional)

No response

[SteveL-MSFT]

As long as the result of the file.bicepparam being run through bicep build-params results in a valid DSC template, it should just work since the bicepparam extension gets invoked whether it's a parameter file or config file.

[Gijsreyn]

I think the big difference with the mentioned commands above is that it does twice: once for the template file itself andthe parameter file:

I'm not sure if we want to mimic the same behaviour in the CLI. It was just a suggestion :)