[tasks] Fix deduplication key collisions and crash on nested data

[atheendre130505]

This PR resolves two critical logic issues in the deduplication utilities within
augur/tasks/util/worker_util.py:

Key Collision: Replaced underscore-joined string keys with tuple-based keys in remove_duplicates_by_uniques
to prevent false duplicates when field values contain underscores or when distinguishing between None and "None".
TypeError Crash: Introduced a recursive _make_hashable helper function to handle nested unhashable structures (dictionaries and lists), preventing crashes in remove_duplicate_dicts and remove_duplicates_by_uniques.

This PR fixes #3632

Notes for Reviewers
The fix incorporates a new internal helper _make_hashable that ensures any nested data structure is converted to a sorted, immutable tuple before being used as a set or dictionary key. Rigorous edge case testing was performed to verify that boundary collisions (e.g., {"a": "foo_bar", "b": "baz"} vs {"a": "foo", "b": "bar_baz"}) are now handled correctly.

All original imports and the existing heading structure of the file have been preserved.
Signed commits

Yes, I signed my commits.
Signed-off-by:atheendre130505 atheendre@gmail.com

[shlokgilda]

Tuple-based keys fix the theoretical collision, _make_hashable handles nested structures, and the new remove_duplicate_dicts is actually better than the original since it preserves insertion order (the old set() approach didn't). Although, I am not sure if we even want to add these change considering the fact that this is a defensive pattern. We can discuss this further in the issue #3632.