cs_log_set_filter() is removed in favor of cs_log_set_file_level() which
allows setting log verbosity of individual files and/or lines.

E.g.: `mg_=1,mjs=1,=4` - level for for everything except mjs and mongoose.

We use the fact that we are usually pretty careful with our file names and use prefixes consistently.

In mos, `debug.file_level` sets the option on boot and `Sys.SetDebug` is updated to parse `file_level` option to change it at runtime.

CL: Log file:line instead of function; add cs_log_set_file_level()

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