implement batch document optimization for text embedding processor

[will-hwang]

Description

This PR includes changes for:

1. refactor of InferenceFilter to simplify logic for copying embeddings
2. implementation for batch document update by overriding TextEmbeddingProcessor's batchExecute method in its parent class AbstractBatchingProcessor

Proposed State [Batch Document Update]

Steps:

1. Process Maps are generated for each IngestDocument based on the Field Map defined.
2. If skip_existing feature is set to true, filter the process map for each IngestDocument.
   1. Existing documents are fetched via OpenSearch client’s Multi-Get Action to compare each of the existing inference text against its corresponding IngestDocument
      1. if documents do not exist, or any exception is thrown, fallback to calling model inference
   2. Locate the embedding fields in each existing document
      1. Recursively traverse the process map to find embedding fields. Keeping track of the traversal path is required for look up in existing document.
      2. Once embedding fields are found, attempt to copy embeddings from existing document to its corresponding ingest document.
   3. If eligible, copy over the vector embeddings from existing document to its corresponding ingest document
      1. It is eligible for copy if inference text in ingest document and its corresponding existing document is the same, and embeddings for the inference text exist in its existing document.
      2. Note, if in case of values in list, the fields in the same index are compared to determine text equality
   4. If eligible fields have been copied, remove the entry in process map
3. Inference List is generated based on entries in Filtered Process Map.
4. ML Commons InferenceSentence API is invoked with filtered inference list.
5. Embeddings for filtered inference list are generated in ML Commons.
6. Embeddings for filtered inference list are mapped to target fields via entries defined in process map.
7. Embeddings for filtered inference list are populated to target fields in IngestDocument.

Related Issues

HLD: #1138

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.56%. Comparing base (1a6e58e) to head (516c43a).

Additional details and impacted files

@@                    Coverage Diff                    @@
##             optimized-processor    #1217      +/-   ##
=========================================================
- Coverage                  81.94%   81.56%   -0.39%     
+ Complexity                  2604     1311    -1293     
=========================================================
  Files                        194       97      -97     
  Lines                       8858     4496    -4362     
  Branches                    1498      762     -736     
=========================================================
- Hits                        7259     3667    -3592     
+ Misses                      1016      534     -482     
+ Partials                     583      295     -288     

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