Move BitPacked serde logic from VTable to Plugin

[mhk197]

Move metadata, serialization and deserialization of fastlanes.bitpacked into BitPackedPlugin. The VTable retains only the required error-returning serde methods and in-memory array validation. BitPackedPlugin is registered on the default session instead of the vtable-derived plugin by default.

Users must now register BitPackedPlugin instead of BitPacked on session.

This refactor is made in preparation for introducing a new version of BitPackedArray

[codspeed]

Merging this PR will not alter performance

⚠️ 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.

⚠️ 1 benchmark measured no execution time

Nothing ran under measurement, usually because the compiler removed the code under test. This result is not comparable, so it counts as unchanged.

Preventing compiler optimizations

✅ 2085 untouched benchmarks
⏩ 503 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚠️	Simulation	bench_compare_sliced_dict_primitive[(3333, 10000)]	< 1 ns	< 1 ns	N/A

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_{Comparing mk/bitpacked-stack-01-wire-boundary (0cd02cd) with develop (4224390)²}

Footnotes

1. 503 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. No successful run was found on develop (0751940) during the generation of this report, so 4224390 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩