refactor: improve RunPod client

- Refactor RunPod client to use generics for requests and
responses.
- This improves code readability and maintainability.
- Remove redundant code for building GraphQL queries and
handling HTTP requests.
- Add support for environment variables in pod creation.
- Update example with new API key and environment variables.

Co-authored-by: supermario <mariobassem12@gmail.com>

lib/core/httpconnection/connection_methods_generic.v

@@ -9,6 +9,7 @@ pub fn (mut h HTTPConnection) get_json_generic[T](req Request) !T {
 
 pub fn (mut h HTTPConnection) post_json_generic[T](req Request) !T {
 	data := h.post_json_str(req)!
+	println('data: ${data}')
 	return json.decode(T, data) or { return error("couldn't decode json for ${req} for ${data}") }
 }