Logic in `main_namemap_validate_and_fix` could end up re-generating
a thousand of time the names of IDs because of an invalid assumption
about processed IDs being re-processable (in case they get renamed).
Also do not `CLOG_ERROR` when checking and fixing errors, if this code is
called to fix errors, it means errors are expected. Use `CLOG_INFO`
instead, or `CLOG_WARN` when the info is really important (like when IDs
had to be renamed).
And finally, simplify code clearing invalid namemaps, there is now a
function to handle this task, `BKE_main_namemap_clear`.
Issues & improvements found while working on readfile errors when
opening `lib/tests/libraries_and_linking/libraries/main_scene.blend`.
e260bc64da