refactor: cleanup context (#1816)
* Removes NewRequestWithContext.
* Moves cgi logic to cgi.go
* Calls 'update_request_info' from the C side.
* Calls 'update_request_info' from the C side.
* clang-format
* Removes unnecessary export.
* Adds TODO.
* Adds TODO.
* Removes 'is_worker_thread'
* Shortens return statement.
* Removes the context refactor.
* adjusts comment.
* Skips parsing cgi path variables on explicitly assigned worker.
* suggesions by @dunglas.
* Re-introduces 'is_worker_thread'.
* More formatting.
