Add calculate-recall parameter to vector search and skip calculating recall if number clients > cpu cores

[finnroblin]

Description

When the number of search clients is greater than the number of cpu cores recall drops unexpectedly. @VijayanB is investigating the cause, but this PR throws a warning if num_clients > the cpu cores available and skips calculating the recall. It also adds a parameter calculate-recall to specify whether or not to calculate recall (either calculate-recall: true or calculate-recall: false).

Testing

• New functionality includes testing

Unit tests.
Also tested on mac with 12 cores. Skips recall calculation if num_clients > 12, calculates recall otherwise. calculate-recall parameter works as expected. Will add unit tests in a second PR by EOD.

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[IanHoang]

Had a sync with @VijayanB and @gkamat offline. We'll work with @VijayanB to better understand the issue and root cause it. Closing this as of no activity. Feel free to reopen if needed.