Add ArcSwapMap and use it throughout our session registries

[robert3005]

ArcSwap is faster than a lock for read. These session are mutable but mutations
are rare and retrievals are common

[codspeed-hq]

Merging this PR will degrade performance by 14.19%

⚠️ 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 improved benchmark
❌ 4 regressed benchmarks
✅ 1270 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	chunked_bool_canonical_into[(1000, 10)]	30.3 µs	45.5 µs	-33.28%
❌	Simulation	chunked_varbinview_canonical_into[(1000, 10)]	161.5 µs	197.8 µs	-18.33%
❌	Simulation	chunked_varbinview_into_canonical[(1000, 10)]	176.1 µs	212.4 µs	-17.09%
❌	Simulation	bitwise_not_vortex_buffer_mut[128]	246.1 ns	275.3 ns	-10.6%
⚡	Simulation	take_map[(0.1, 1.0)]	1.9 ms	1.7 ms	+15.19%

Tip

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

---

_{Comparing rk/aggregatearcswap (1626b3c) with develop (b29b2b9)}

[joseph-isaacs]

Shall we have a pattern like this for ArcSwap?

[joseph-isaacs]

Can we break this out into a pattern with a struct or type wrapper?

[robert3005]

I will make a follow up.

[robert3005]

Looks like this broke the backcompat check https://github.com/vortex-data/vortex/actions/runs/26544463401/job/78201950621?pr=8072. Need to investigate this tomorrow as it's passing locally