fix: dev: Save configuration as text

fix: dev: Save configuration as text

A `cfg_obj_t` object tree structure takes up considerably more space than the equivalent canonical text. If `allow-new-zones` is disabled and catalog zones are not in use, then we don't need the object tree. By storing the configuration in text format, we can use less memory, and `rndc showconf` and `rndc showzone` still work.

Merge branch 'each-cfg-as-text' into 'main'

See merge request isc-projects/bind9!11236