Refactor MS MARCO passage dev with Cohere V3 embeddings

[lintool]

Added int8 indexes, general clean-up, added links to README.

@cadurosar we're missing dl19/dl20 - what do you want to do? Send in separate PR?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f86a65f) 65.66% compared to head (7f68cf5) 65.66%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #2366   +/-   ##
=========================================
  Coverage     65.66%   65.66%           
  Complexity     1398     1398           
=========================================
  Files           207      207           
  Lines         11631    11631           
  Branches       1471     1471           
=========================================
  Hits           7637     7637           
  Misses         3484     3484           
  Partials        510      510           

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[lintool]

@cadurosar says we should go ahead and merge this, and circle back to add dl19/dl20 later.

@jasper-xian will wait for your CR first.