The `operator debug` command writes JSON files from API responses as a single
line containing an array of JSON objects. But some of these files can be
extremely large (GB's) for large production clusters, which makes it difficult
to parse them using typical line-oriented Unix command line tools that can
stream their inputs without consuming a lot of memory.

For collections that are typically large, instead emit newline-delimited JSON.

This changeset includes some first-pass refactoring of this command. It breaks
up monolithic methods that validate a path, create a file, serialize objects,
and write them to disk into smaller functions, some of which can now be
standalone to take advantage of generics.