ffi: remove vx_file scan

[myrrc]

Users should use vx_data_source and vx_scan.
write_array is retained until we have proper file writing FFI

[codspeed-hq]

Merging this PR will improve performance by 19.84%

⚠️ 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
✅ 1265 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	chunked_varbinview_opt_canonical_into[(1000, 10)]	225.4 µs	188.1 µs	+19.84%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing myrrc/ffi-rm-old-scan (f19d8fa) with develop (6e6fb1d)}