linux: Quiet some noisy logs when logging to file (#13260)

zbus, naga, and some parts of blade are pretty noisy at the INFO level.
zbus especially dumps large debug dumps into the logs.

So on Linux, when logging to a file, we reduce that noise. That means
one still gets the full firehose when doing `RUST_LOG=info cargo run`,
but not in the logs.


Release Notes:

- N/A