Revert #764 to only use shadowjar publication

[peterzhuamazon]

Description

Revert #764 to only use shadowjar publication.

ml used to publish a lot of unrelated content in jar, therefore this PR is created to only publish related classes:
#764

However, the added jars publication alongside shadow caused some race conditions, so the github actions task was switched back to using shadow, without removing jars publication in #764.
#779

The above race condition in gradle 7 is not observed clearly when building non-snapshot artifacts with scripts/build.sh but showing clear race conditions in gradle 8 after this PR:
#892

The initial fix to this issue in #957 is not correct as it switch from shadow to jars, the exact same error spawns the fix of github actions in #779, causing dependent plugin such as neural-search failed with this error:

* What went wrong:
Execution failed for task ':bundlePlugin'.
> Could not resolve all files for configuration ':runtimeClasspath'.
   > Could not find org.opensearch:opensearch-ml-common:2.8.0.0.
     Searched in the following locations:
       - https://repo.maven.apache.org/maven2/org/opensearch/opensearch-ml-common/2.8.0.0/opensearch-ml-common-2.8.0.0.pom
       - file:/usr/share/opensearch/.m2/repository/org/opensearch/opensearch-ml-common/2.8.0.0/opensearch-ml-common-2.8.0.0.pom
       - https://aws.oss.sonatype.org/content/repositories/snapshots/org/opensearch/opensearch-ml-common/2.8.0.0/opensearch-ml-common-2.8.0.0.pom
       - https://plugins.gradle.org/m2/org/opensearch/opensearch-ml-common/2.8.0.0/opensearch-ml-common-2.8.0.0.pom
     Required by:
         project : > org.opensearch:opensearch-ml-client:2.8.0.0

* Try:

> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
* Get more help at https://help.gradle.org/

Plus, the issue observed in #764 has since been resolved by #796.

Therefore, the final fix to this issue is to remove the jars publication all together.

Issues Resolved

opensearch-project/opensearch-build#3434

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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]

Codecov Report

Merging #959 (91370a7) into 2.x (eb94584) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                2.x     #959   +/-   ##
=========================================
  Coverage     82.32%   82.32%           
  Complexity     1918     1918           
=========================================
  Files           149      149           
  Lines          7506     7506           
  Branches        750      750           
=========================================
  Hits           6179     6179           
  Misses          987      987           
  Partials        340      340           

Flag	Coverage Δ
ml-commons	82.32% <ø> (ø)

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