[Feature/extensions] Removed opensearchplugin and extension runs independently

[owaiskazi19]

Signed-off-by: Owais Kazi owaiskazi19@gmail.com

Description

This PR makes the extension run independently and removes the dependency on opensearchplugin. For now tasks such as publishing and bundlePlugin are taken care of. integTest will be done by creating a new framework for integration tests here opensearch-project/opensearch-sdk-java#120. The remaining tasks are P1 and will be done in opensearch-project/opensearch-sdk-java#144.

It also integrates the local published SDK with AD build.gradle and has a main class to run the extension from.
For now, the sample RestHandler is integrated but later with opensearch-project/opensearch-sdk-java#58 it will be replaced with create Index.

Companion PR on OpenSearch: opensearch-project/OpenSearch#4556
SDK: opensearch-project/opensearch-sdk-java#153

Issues Resolved

opensearch-project/opensearch-sdk-java#133 and opensearch-project/opensearch-sdk-java#137

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[codecov-commenter]

Codecov Report

Merging #672 (be1f70b) into feature/extensions (11d094a) will decrease coverage by 0.15%.
The diff coverage is 0.00%.

@@                   Coverage Diff                    @@
##             feature/extensions     #672      +/-   ##
========================================================
- Coverage                 53.81%   53.66%   -0.16%     
+ Complexity                 2679     2676       -3     
========================================================
  Files                       288      290       +2     
  Lines                     16004    16032      +28     
  Branches                   1703     1706       +3     
========================================================
- Hits                       8612     8603       -9     
- Misses                     6767     6801      +34     
- Partials                    625      628       +3     

Flag	Coverage Δ
plugin	53.66% <0.00%> (-0.16%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...va/org/opensearch/ad/AnomalyDetectorExtension.java	0.00% <0.00%> (ø)
...g/opensearch/ad/rest/RestCreateDetectorAction.java	0.00% <0.00%> (ø)
.../java/org/opensearch/ad/AnomalyDetectorRunner.java	36.90% <0.00%> (-5.96%)	⬇️
.../main/java/org/opensearch/ad/ml/CheckpointDao.java	69.55% <0.00%> (-0.65%)	⬇️
...c/main/java/org/opensearch/ad/util/ParseUtils.java	60.43% <0.00%> (-0.15%)	⬇️
...ain/java/org/opensearch/ad/model/ModelProfile.java	70.90% <0.00%> (ø)
...ava/org/opensearch/ad/model/TimeConfiguration.java	100.00% <0.00%> (ø)