fix: dev: Silence all warnings that stem from the default config

As we now setup the logging very early, parsing the default config would always print warnings about experimental (and possibly deprecated) options in the default config. This would even mess with commands like named -V and it is also wrong to warn users about using experimental options in the default config, because they can't do anything about this. Add CFG_PCTX_NODEPRECATED and CFG_PCTX_NOEXPERIMENTAL options that we can pass to cfg parser and silence the early warnings caused by using experimental options in the default config.