Allow configuring log level and format

[FredrikAugust]

Argo rollouts allow setting the log format (text/json) and log level by environment variables, and allow sending args to the plugins as demonstrated by the newest PR #101. It would be great if that was possible with this plugin as well. Even though argo rollouts have a slightly hard-to-parse way to forward the logs from plugins (argoproj/argo-rollouts#4117), this would make it more approachable.

[FredrikAugust]

Also, perhaps

time="2025-02-06T10:34:50Z" level=info msg="[SetWeight] plugin \"argoproj-labs/gatewayAPI\" controls TCPRoutes: []" plugin=trafficrouter

Should be a debug log? It's logged quite frequently as we have 40-50 GRPC/HTTP routes, and when reconciling I believe it prints this for TPC, HTTP and GRPC routes per rollout.