cli, lib, lang: Port to new cli library

The new version of the urfave/cli library is moving to generics, and
it's completely unclear to me why this is an improvement. Their new API
is very complicated to understand, which for me, defeats the purpose of
golang.

In parallel, I needed to do some upcoming cli API refactoring, so this
was a good time to look into new libraries. After a review of the
landscape, I found the alexflint/go-arg library which has a delightfully
elegant API. It does have a few rough edges, but it's otherwise very
usable, and I think it would be straightforward to add features and fix
issues.

Thanks Alex!

lib/main.go

@@ -92,7 +92,7 @@ type Main struct {
 	Sema                   int    // add a semaphore with this lock count to each resource
 	Graphviz               string // output file for graphviz data
 	GraphvizFilter         string // graphviz filter to use
-	ConvergedTimeout       int64  // approximately this many seconds of inactivity means we're in a converged state; -1 to disable
+	ConvergedTimeout       int    // approximately this many seconds of inactivity means we're in a converged state; -1 to disable
 	ConvergedTimeoutNoExit bool   // don't exit on converged timeout
 	ConvergedStatusFile    string // file to append converged status to
 	MaxRuntime             uint   // exit after a maximum of approximately this many seconds