[FEATURE] OpenSearch 1.3 release related changes

[dreamer-89]

As part of OpenSearch 1.3 release, there are changes which needs corresponding update on documentation. Using this issue to track all those changes (issues/PR). A few of them are self explanatory while other needs more inputs from the author around external wordings.

1. Add 'key' field to 'function_score' query function definition in explanation response OpenSearch#1711
2. [Deprecate] index.merge.policy.max_merge_at_once_explicit OpenSearch#1981
3. [Deprecate] Setting explicit version on analysis component OpenSearch#1978
4. [Backport] Enabling Sort Optimization to make use of Lucene OpenSearch#1989
5. Add max_expansions option to wildcard interval OpenSearch#1916
6. Rename field_masking_span to span_field_masking OpenSearch#1606

[dblock]

Looks all done, closing.