feat(stdlib): standard-library BTreeMap collection

[ss2165]

Closes #2082

Codex made

Summary

• Add a BTreeMap collection to the Guppy standard library
• Export the collection through std.collections
• Add integration coverage and project configuration updates

Testing

• Added integration tests for BTreeMap behavior

Open questions

• Should this PR introduce the Ord protocol publicly?
• Tests are very slow - revisit after august'26 performance improvements

[github-actions]

Bencher Report

Project	guppylang
Branch	codex/plan-btreemap-standard-library
Testbed	Linux

Click to view all benchmark results

Benchmark	hugr_bytes	Benchmark Result bytes x 1e3 (Result Δ%)	Upper Boundary bytes x 1e3 (Limit %)	hugr_nodes	Benchmark Result nodes (Result Δ%)	Upper Boundary nodes (Limit %)
tests/benchmarks/test_big_array.py::test_big_array_compile	📈 view plot 🚷 view threshold	66.41 x 1e3 (0.00%) Baseline: 66.41 x 1e3	67.07 x 1e3 (99.01%)	📈 view plot 🚷 view threshold	4,595.00 (0.00%) Baseline: 4,595.00	4,640.95 (99.01%)
tests/benchmarks/test_ctrl_flow.py::test_many_ctrl_flow_compile	📈 view plot 🚷 view threshold	28.77 x 1e3 (0.00%) Baseline: 28.77 x 1e3	29.06 x 1e3 (99.01%)	📈 view plot 🚷 view threshold	1,301.00 (0.00%) Baseline: 1,301.00	1,314.01 (99.01%)
tests/benchmarks/test_queue_push_pop.py::test_queue_push_benchmark_compile	📈 view plot 🚷 view threshold	7.84 x 1e3 (0.00%) Baseline: 7.84 x 1e3	7.92 x 1e3 (99.01%)	📈 view plot 🚷 view threshold	310.00 (0.00%) Baseline: 310.00	313.10 (99.01%)
tests/benchmarks/test_queue_push_pop.py::test_queue_push_pop_benchmark_compile	📈 view plot 🚷 view threshold	10.78 x 1e3 (+0.01%) Baseline: 10.77 x 1e3	10.88 x 1e3 (99.02%)	📈 view plot 🚷 view threshold	411.00 (0.00%) Baseline: 411.00	415.11 (99.01%)

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 22.82609% with 497 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.24%. Comparing base (9ef99cd) to head (7fcaf76).

Files with missing lines	Patch %	Lines
...ppylang/src/guppylang/std/collections/btree_map.py	22.70%	497 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2083      +/-   ##
==========================================
- Coverage   93.19%   90.24%   -2.96%     
==========================================
  Files         152      153       +1     
  Lines       14647    15291     +644     
==========================================
+ Hits        13651    13799     +148     
- Misses        996     1492     +496     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 11 untouched benchmarks

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_{Comparing codex/plan-btreemap-standard-library (7fcaf76) with main (9ef99cd)}