Remove benchmarks folder from k-NN repo

[navneet1v]

Description

Remove benchmarks folder from k-NN repo. The removal is needed because of below reasons:

1. The workloads have been moved to https://github.com/opensearch-project/opensearch-benchmark-workloads/tree/main/vectorsearch and no updates will be added on these tools.
2. The python dependencies in code creates CVEs and needs to be regularly updated. Since we no longer use these tools its better to remove the tools.

Related Issues

#1954, #1831, #1830, #1786, #1698, #1687

Check List

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[naveentatikonda]

As a backup, last month I created this branch out of main branch for the benchmarks
https://github.com/opensearch-project/k-NN/tree/knn-benchmarks

[naveentatikonda]

As a backup, last month I created this branch out of main branch for the benchmarks https://github.com/opensearch-project/k-NN/tree/knn-benchmarks

Just saw that Navneet created another branch old-benchmarks for backup. I will delete the knn-benchmarks branch