Runs the full set of MAML validity checks (a table: key, at least one
field, a valid data_type on every field, ...) against either an
already-loaded MAML passed as maml (a parquet_maml_file, e.g. via
parquet_load_maml_file or built in memory) or a MAML filename passed
as maml (a character(len=*) .maml file path, loaded from disk first,
then checked identically).