Compute function test harness

[gatesn]

We should write a test harness for each compute function. It should ask the encoding for arrays of various dtype, length, nullability etc.

This code can be feature flagged behind a custom test-harness feature, for which there's a funky workaround to allow the same crate to enable its own optional feature as a dev-dependency. See https://users.rust-lang.org/t/how-to-reference-the-test-of-another-crate-in-the-current-crate/91965/4

[gatesn]

Basic setup is done, we lack coverage amongst all compute functions

[robert3005]

We have coverage for search_sorted and binary_numeric fwiw.

[gatesn]

Closing as stale, each compute function should define a canonical implementation alongside itself (https://github.com/vortex-data/vortex/issues/3454). That means it should be relatively easy to compare results if we also have #1424