Cleanup fastlanes encodings crate #7118

Performance Regression: -10.2%

❌ 1 regressed benchmark
✅ 1015 untouched benchmarks
⏩ 1522 skipped benchmarks¹

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

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`map_each[BufferMut<i32>, 128]`	770.6 ns	858.1 ns	-10.2%

_{Comparing rk/deltaenc (4ccf279) with develop (1c8667c)}

1522 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. ↩