Also remove a debugging statement

TODO: if there are other relevant debug flags, they could go in a class together

Now the rest of them. Also fixes trying to access nonexistent parameter to h_do_parse()

Replaced one instance for profiling

- hammer-parse-apply wasn't clearing the pointer to the desired stack frame
- Reproduction steps: hammer-parse-step N, hammer-parse-apply, hammer-parse-step 1

- Also fixes double curly braces when printing HByte structs when len is 0

Add tests for .set_top_node(0, None), and .set_top_node(None, None)

Also ensure cleanup runs in HParseResult test