Allow Beyla to receiver a logger object

[marctc]

Currently Beyla uses its own logger and it's global to all packages. This is fine using
Beyla as standalone process, but when using Beyla with Alloy the loggers are not the
same and log level can't be propagated properly.

Currently we are using slog.SetDefault to specify the log level and other options.
Ideally Beyla should receive a logger object an propagate to the rest of packages.
Usually Prometheus packages use go-kit logger, but I assume we can do the same
with slog.

[mariomac]

I think this fixes this task, at least partially: #1069