Allow fine-grain logging to be configurable via CLI arguments

*Title*: *Allow fine-grain logging to be configurable via CLI arguments*

*Description*:
> [As discussed in Slack](https://envoyproxy.slack.com/archives/C78M4KW76/p1757343496764639?thread_ts=1757329081.659419&cid=C78M4KW76), it's currently not possible to change the fine-grain logging using CLI arguments. Currently it can only be configured via an admin endpoint. This is inconvenient because when deploying on Kubernetes, I can't easily configure the fine-grain logging building a container of my own. It's difficult (or at the very best a hack like a `postStart` with a sleep) to do it with a plain `envoy` image.

*Suggestion*:
The suggestion given in Slack that @paul-r-gall and @botengyao seemed to prefer was the following:

Rather than having `--enable-fine-grain-logging` it would take configuration similar to `--component-log-level`, so something like `--fine-grain-log-level(s) `.