[Backport 2.x] Drop Index Implementation

[opensearch-trigger-bot]

Backport 5df6105 from #2204.

[codecov]

Codecov Report

Merging #2217 (f5f1c39) into 2.x (e58af26) will decrease coverage by 0.20%.
The diff coverage is 73.58%.

@@             Coverage Diff              @@
##                2.x    #2217      +/-   ##
============================================
- Coverage     96.61%   96.41%   -0.20%     
- Complexity     4751     4759       +8     
============================================
  Files           438      440       +2     
  Lines         12742    12817      +75     
  Branches        869      872       +3     
============================================
+ Hits          12311    12358      +47     
- Misses          422      450      +28     
  Partials          9        9              

Flag	Coverage Δ
sql-engine	96.41% <73.58%> (-0.20%)	⬇️

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Files	Coverage Δ
...park/asyncquery/AsyncQueryExecutorServiceImpl.java	100.00% <100.00%> (ø)
.../spark/asyncquery/model/AsyncQueryJobMetadata.java	88.88% <100.00%> (+3.70%)	⬆️
...rch/sql/spark/dispatcher/SparkQueryDispatcher.java	100.00% <100.00%> (ø)
.../org/opensearch/sql/spark/utils/SQLQueryUtils.java	100.00% <100.00%> (ø)
...org/opensearch/sql/spark/flint/FlintIndexType.java	92.85% <92.85%> (ø)
.../sql/spark/flint/FlintIndexMetadataReaderImpl.java	0.00% <0.00%> (ø)