reduce k value to result count

[tomhamer]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  we reduce k to equal the result count, which vastly improves search latency. Since we have moved to lucene we no longer see the error with inner hits not being returned

• What is the current behavior? (You can also link to an open issue here)
  Search latency is very high due to a high k - this is a problem since we moved from NMSLIB to lucene based search.

• What is the new behavior (if this is a feature change)?
  Reduces search lateny on large indexes by approx 20x.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  no

• Have unit tests been run against this PR? (Has there also been any additional testing?)

• Related Python client changes (link commit/PR here)

• Related documentation changes (link commit/PR here)

• Other information:

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added / updated (for bug fixes / features)

[pandu-k]

This change results in a failing unit test: https://github.com/marqo-ai/marqo/actions/runs/3671015792/jobs/6205945452#step:8:3873

This unit test is regarding protections for when result_count gets too big (over 10k).

This hits the k limit of Marqo-os.

Suggestion:
- Correct the test (perhaps by mocking Marqo-os via mocking a GET request)
- Set the default for this limit to the Marqo-os limit (for the best user experience):

marqo/src/marqo/tensor_search/configs.py

Line 35 in bb54a78

EnvVars.MARQO_MAX_RETRIEVABLE_DOCS: None,

Also, what are the implications for a large result_count (result_count > 500)? For small Ks this change would result in a speed-up, but latency is probably degraded for these large cases

[pandu-k]

Code to test the impact of missing inner hits:

• An OpenSearch community member's gist
• OpenSearch contributor's gist

[pandu-k]

Tested for missing inner hits. None retrieved

[pandu-k]

Ran test suite, all passed