Randomize KNN vector format parameters in tests

[msokolov]

Description

I discovered while doing some sweeping refactoring changes that we lack coverage of many vector field features, like scalar compression and concurrent merging. We even lack randomization for basic settings like graph connectivity (we always test with the default = 32).

The idea here is to add randomization to RandomCodec similar to what we do for other field types. I made an initial, but many tests do make assumptions that were broken. I think initially we will need a way to "opt out" of such randomization. Is there a standard way to do that (for a specific format, or for the whole codec)?

Gradle command to reproduce

No response

[msokolov]

also pushed 4f8035c to address a build failure by disabling randomization in more tests