Bug 1693495 - [devtools] Implement a beginning of "Network" commands, starting with sendHTTPRequest. r=devtools-reviewers,nchevobbe

Use new "commands" thunk argument.
We were passing connector as argument whereas we could have fetched it from thunk arguments.

This will help slowly convert Connector/NetMonitorAPI to a command.

Differential Revision: https://phabricator.services.mozilla.com/D166055