Remove secondary level filtering in debug_output(). Now the only filter
is debug_should_output() (per-category + global fallback). Output goes
to file (if file_output set) or console (if console_enabled), with no
additional level check.
Removed:
- debug_set_console_level(), debug_set_file_level()
- console_level, file_level fields from debug_config_t
- debug_set_level() no longer sets console_level