[DRAFT] refactor query graph to make it more useful

[guillesd]

The idea of this PR is to make this tool a bit more useful (and visually appealing). I think generally it is good to have some better profiling tools to explore queries.

To use the tool:

1. Build this branch (see https://duckdb.org/docs/stable/dev/building/python)
2. Run the following in DuckDB

PRAGMA enable_profiling = 'json';
PRAGMA profiling_output = './tmp/profile.json';
SELECT ... FROM ...;

3. Run the script (I do it with uv):

uv run python -m duckdb.query_graph tmp/complex_profile.json

Which should yield something like the following screenshot: