Add query parameters to http_probe

[sjmalnati]

Add an option to http_probe for query parameters.

For my use case I need to probe an API that takes in the API key as a query parameter. Normally, query parameters are included as part of the target in Prometheus configuration, but Prometheus configuration is exposed in its UI portal, and I do not want to expose API keys.

In addition to having an option for query parameters there should be an option to source the query params from a file so it can be a k8s secret. This would be analogous to this issue for request body: #391 or would be covered by having the entire module config be from a file: #1048.