[DOC] Lucene Inbuilt Scalar Quantizer to quantize float 32 bits to 4 bits

[naveentatikonda]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request.
Since OpenSearch 2.17 we have support for Lucene Inbuilt Scalar Quantizer which accepts fp32 vectors as input and dynamically quantizes the data into int7 ranging from [0 to 127] providing 4x compression. Adding support for 4 bits to the Lucene SQ provides 8x compression which helps to quantize fp32 vectors into int4 ranging from [0 to 15], which helps to further reduce the memory requirements by trading off recall.

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.
2.19

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
opensearch-project/k-NN#2252