Move to maturin as a Build System

[riesentoaster]

Reason: scikit-build-core was just creating too many problems. We still want a parallel build. As a nice side effect, this also prepares the ability to write hot-path performance-critical parts in Rust.

Changes:

• Build the parser with cargo's cc module
• Write a small Rust wrapper around the C++ parser to make it accessible to Python
• Introduce a dummy Rust function to show access for future functions
• Ensure type synchronization between Rust and Python
• Remove the no longer needed FANDANGO_SKIP_CPP_PARSER (and FANDANGO_REQUIRE_BINARY_BUILD) — we always build on developer machines and will have to do this as soon as we move anything serious to Rust; consumers download binaries anyway, they don't need the toolchain

[github-actions]

Bencher Report

Branch	chore/manturin
Testbed	ubuntu-latest

Click to view all benchmark results

Benchmark	Latency	Benchmark Result milliseconds (ms) (Result Δ%)	Upper Boundary milliseconds (ms) (Limit %)
tests/test_benchmarks.py::test_generate_with_single_hard_constraint	📈 view plot 🚷 view threshold	1,464.75 ms (-23.76%) Baseline: 1,921.33 ms	2,124.20 ms (68.96%)
tests/test_benchmarks.py::test_generate_with_single_soft_constraint	📈 view plot 🚷 view threshold	68,989.80 ms (+22.97%) Baseline: 56,103.05 ms	87,573.95 ms (78.78%)
tests/test_benchmarks.py::test_init_fandango	📈 view plot 🚷 view threshold	136.58 ms (-10.28%) Baseline: 152.23 ms	166.84 ms (81.86%)
tests/test_benchmarks.py::test_parse_spec	📈 view plot 🚷 view threshold	136.94 ms (-10.51%) Baseline: 153.03 ms	166.60 ms (82.20%)

🐰 View full continuous benchmarking report in Bencher

[riesentoaster]

(CodeQL is still broken for now because it can no longer auto-detect the build system. We would need to either just drop it or provide a custom config, but that's definitely doable.)