Mittens should ingest from a file not args

[tehlers320]

Describe the feature
When running in kubernetes at scale, mittens makes the pod objects gigantic. This causes k8s clusters to fail/timeout/delay actions at high scale.

Here is one example of a use-case and how much data flows thru all cluster operators + api server itself.

kubectl -n my-namespace mypod -o yaml | yq .spec.containers[].args |wc -c
  133100

Even when not degrading clusters, this leads to high cpu use and in some cases memory use on operators adding cost to operating.

It looks like this:

mittens/cmd/flags/target.go

Line 47 in 6446db6

flag.StringVar(&t.HTTPProtocol, "target-http-protocol", string(http.HTTP1), "Protocol used for HTTP requests")

could be dropped in favor of viper and allow both.

Rational

To keep clusters stable when running at high scale with a lot of churn.

Example Scenario

If it applies, use cases where the feature be used.