Ast to ruff

[seddonym]

Replaces the use of Python's built in ast module with Ruff's parser. Credit to @Peter554!

The main reason for doing this is to pave the way to move more of the graph building into Rust - but it is also faster right now, especially with multiprocessing turned off. I'm not sure why Codspeed is showing degraded performance.

Based on #214 (which had some conflicts that I needed to resolve).

Comparison

On my local machine, on a large repository, here's a comparison of how long it takes to build the graph.

Existing (AST)

• No multiprocessing: 45s
• Multiprocessing: 13s

This branch (Ruff)

• No multiprocessing: 15s
• Multiprocessing: 8s

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #216 will degrade performances by 14.84%

_{Comparing ast-to-ruff (dc502f3) with master (810bb16)}

Summary

⚡ 2 improvements
❌ 3 regressions
✅ 17 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	test_deep_layers_large_graph_kept	16.3 ms	19.1 ms	-14.84%
❌	test_no_chain	1.1 ms	1.2 ms	-11.11%
❌	test_no_chains	1.1 ms	1.2 ms	-11.08%
⚡	test_build_django_from_cache_a_few_misses[15]	381.5 ms	162.2 ms	×2.4
⚡	test_build_django_from_cache_a_few_misses[2]	167.8 ms	138.4 ms	+21.2%