refactor: further logger clean-up

[KristjanESPERANTO]

After #4049 here are two small follow-up improvements to js/logger.js.

1. Simpler bind syntax — Function.prototype.bind.call(console.debug, console) is an archaic pattern. The equivalent console.debug.bind(console) works fine in all supported engines (Node.js ≥ 22, modern browsers) and is much easier to read. Also: console.timeStamp exists in all supported environments, so the conditional fallback to an empty function is no longer needed.

2. Simpler setLogLevel — instead of iterating over all keys in the logger object and permanently overwriting them, the method now loops over the five log-level keys explicitly and rebinds from console[key]. This makes the filtered set obvious at a glance and ensures utility methods like group, time, and timeStamp are never accidentally silenced — they're structural helpers, not log levels.