Search contents for pattern (optional path / glob filters).
The glob filter uses fnmatch semantics and does not follow the
shared include-glob contract that glob() on this class uses: *
crosses /, and matching is case-normalized. Do not assume the two
agree on a given pattern.
When max_count is set, at most that many matches are returned; if more
exist the search stops and the result is flagged truncated=True.
Exactly max_count matches with none dropped is reported complete
(truncated=False).
