* eth, cmd: allow FdLimit to be set in config/command line (#24148)

* eth/ethconfig: format code

* cmd, eth/ethconfig: simplify fdlimit arg, disallow toml

* cnd/utils: make fdlimit setting nicer on the logs
Co-authored-by: Gary Rong <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>