feat(codspeed): collect Rust toolchain environment at build time

[GuillaumeLagrange]

Capture rustc and cargo version information during compilation via build.rs and register it through the instrument-hooks environment API at runtime. This enables tracking which toolchain was used to compile benchmarks.

• Update instrument-hooks submodule to get set_environment/write_environment API
• Regenerate FFI bindings for new environment functions
• Add set_environment/write_environment wrappers to InstrumentHooks
• Collect rustc (version, host, release, LLVM version) and cargo version at build time via env vars, register them during InstrumentHooks init
• Always initialize InstrumentHooks (even in Valgrind mode) for env collection

Generated with AI Agent (Claude Code)

[codspeed-hq]

Merging this PR will degrade performance by 28.08%

⚡ 25 improved benchmarks
❌ 18 regressed benchmarks
✅ 532 untouched benchmarks

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

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	WallTime	iter_with_setup	44 ns	40 ns	+10%
❌	WallTime	iter_batched_ref_large_input	44 ns	48 ns	-8.33%
⚡	WallTime	from_elem_decimal[1024]	84 ns	81 ns	+3.7%
⚡	WallTime	iter_batched_per_iteration	44 ns	40 ns	+10%
⚡	WallTime	slice_into_vec_with_bytes	94 ns	56 ns	+67.86%
❌	WallTime	graph_coloring[4]	962 ns	1,073 ns	-10.34%
❌	WallTime	generate_combinations[9]	5.2 µs	7.2 µs	-28.08%
❌	WallTime	string_copy_with_bytes_counter	56 ns	59 ns	-5.08%
⚡	WallTime	generate_combinations[5]	1.5 µs	1.2 µs	+26.28%
⚡	WallTime	fib_in_thread_bench[32]	17.8 ms	16.3 ms	+9.28%
⚡	WallTime	fib_in_thread_bench_local[30]	7 ms	6.5 ms	+8.93%
⚡	WallTime	fib_in_thread[30]	7 ms	6.5 ms	+8.93%
⚡	WallTime	bench_array2[42]	51 ns	47 ns	+8.51%
⚡	WallTime	fibo_10	2 ns	1 ns	×2
⚡	WallTime	bench_array2[10]	29 ns	9 ns	×3.2
⚡	WallTime	fib_in_thread_bench[31]	11.1 ms	10.2 ms	+8.96%
⚡	WallTime	fib_in_thread_bench_local[31]	11.1 ms	10.2 ms	+8.95%
⚡	WallTime	fib_in_thread_bench_local[32]	17.8 ms	16.3 ms	+9.23%
⚡	WallTime	fib_in_thread[32]	17.8 ms	16.3 ms	+9.32%
⚡	WallTime	fib_in_thread[31]	11.2 ms	10.2 ms	+9.32%
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

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_{Comparing cod-2415-implement-toolchain-harvesting-for-rust (8637676) with main (dccf5f4)}