Implement an abstraction that opens file for auditing multiple times, once for every auditing rayon thread

[nazar-pc]

This seems to be a tiny bit faster on Linux, but more importantly, it is faster than even memory-mapped I/O on Windows.

Specifically numbers I shared on Rust Internals are:

• 936 ms for single file with seek_read (+handling of partial reads identically to read_exact_at in std)
• 245 ms for single file with memory-mapped I/O
• 190 ms with file openes many times, once for each thead in thread pool using seek_read

Will ask come community members to bench it as well.

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