Remove the unstable encodings feature

[robert3005]

unstable_encodings was only ever necessary to let us try things out without immediately introducing stability guarantees. We have editions now, that's the way things should be restricted, not via compile flags

[codspeed-hq]

Merging this PR will regress 2 benchmarks

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
❌ 2 regressed benchmarks
✅ 2208 untouched benchmarks
⏩ 164 skipped benchmarks¹
🗄️ 1 archived benchmark run²

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	random_i8[0.5]	66.2 µs	90.6 µs	-26.94%
❌	Simulation	decompress[u64, (4000, 1024)]	69.8 µs	85.6 µs	-18.4%
⚡	Simulation	random_i8[0.8]	97.5 µs	68.8 µs	+41.57%
⚡	WallTime	words_gather_dispatch_avx512[1024]	9 ns	7 ns	+28.57%
⚡	Simulation	allocate_drop_bytes[0]	520.2 ns	466 ns	+11.62%
⚡	WallTime	mul_u32_nonnull_avx512	6.3 µs	5.6 µs	+11.46%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing rk/remove-unstable-encodings (b599fdd) with develop (98dd977)³}

Footnotes

1. 164 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. 1 benchmark was run, but is now archived. If it was deleted in another branch, consider rebasing to remove it from the report. Instead if it was added back, click here to restore it. ↩

3. No successful run was found on develop (792cef7) during the generation of this report, so 98dd977 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩