Speed up fixed-sized array iteration

[jleibs]

This optimizes iteration of fixed-sized arrays, but restricts them to Primitives, which seems like a reasonable trade-off for now. We can revisit if we find a need for non-primitive fixed-sized arrays at some point in the future.

I introduced a new benchmark in re_query for Vecs as separate from points. Specifically I use 100k vec arrays so make the issue more readily apparent. For arrays of 1k the other query overhead dominates.

New vec bench

Before:

arrow_batch_vecs/insert time:   [22.727 µs 22.776 µs 22.835 µs]
                        thrpt:  [43.793 Gelem/s 43.906 Gelem/s 44.000 Gelem/s]


arrow_batch_vecs/query  time:   [2.4701 ms 2.4797 ms 2.4912 ms]
                        thrpt:  [40.142 Melem/s 40.328 Melem/s 40.484 Melem/s]

After:

arrow_batch_vecs/insert time:   [23.079 µs 23.137 µs 23.205 µs]
                        thrpt:  [43.094 Gelem/s 43.220 Gelem/s 43.329 Gelem/s]
                 change:
                        time:   [+0.5238% +1.5090% +2.4224%] (p = 0.00 < 0.05)
                        thrpt:  [-2.3651% -1.4865% -0.5211%]

arrow_batch_vecs/query  time:   [161.09 µs 161.69 µs 162.38 µs]
                        thrpt:  [615.85 Melem/s 618.45 Melem/s 620.78 Melem/s]
                 change:
                        time:   [-93.518% -93.482% -93.448%] (p = 0.00 < 0.05)
                        thrpt:  [+1426.3% +1434.1% +1442.7%]

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I've added a line to CHANGELOG.md (if this is a big enough change to warrant it)

[jondo2010]

Did we already have this crate in the deps I guess? We should add a note and track the stabilization of the stdlib feature we actually would use instead:

• https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.array_chunks
• Tracking Issue for Iterator::array_chunks rust-lang/rust#100450

[jleibs]

We did -- see the original implementation of FixedSizeArrayField::arrow_deserialize below.

[emilk]

I love this trick :)