Use BOW values projected to dense as stub embeddings for test

[acatav]

Problem

Current stub encoder is flaky and sometimes puts very different texts very close
Also, it's not putting similar text together, only the same text on itself

Solution

Implement stub dense encoder that project bag of words sparse vector to a dense vector

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

Part of the tests framework itself

[igiloh-pinecone]

I'm concerned about the memory usage of the random_matrix.
Isn't there some simpler solution that doesn't require pre-allocating such a huge matrix?

[igiloh-pinecone]

Wait - isn't that a HUGE shape??
It's a dense matrix, isn't it? Won't it take a lot of memory?

[acatav]

I removed the need in actually holding this matrix, for the default dimensions it's few MB but for output dim 1536 it can become larger than we would like. Anyway, we not even holding a matrix any more

[igiloh-pinecone]

LG(engouh)TM