Remove MaskMut and unused functions from BitBufferMut

[robert3005]

A lot of this logic dates back to earlier expriments. We don't need this logic
and in some cases it's duplicate with a logic we have optimised elsewhere

Signed-off-by: Robert Kruszewski github@robertk.io

[codspeed-hq]

Merging this PR will degrade performance by 11.03%

❌ 3 regressed benchmarks
✅ 1119 untouched benchmarks
⏩ 1455 skipped benchmarks¹

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

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	true_count_arrow_buffer[128]	726.4 ns	813.9 ns	-10.75%
❌	Simulation	true_count_arrow_buffer[1024]	940.8 ns	1,057.5 ns	-11.03%
❌	Simulation	true_count_arrow_buffer[2048]	1 µs	1.1 µs	-10.34%

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_{Comparing rk/nomaskmut (b56c88e) with develop (7618c23)}

Footnotes

1. 1455 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. ↩