[Release 3.0.0] Bump Version to 3.0.0-alpha1 and and updated shadowPlugin

[vaibhoag]

Description

[Release 3.0.0] Bump Version 3.0.0.0-alpha1 and and updated shadowPlugin

• Updated opensearch_version from '3.0.0' to '3.0.0-alpha1'
• Migrated shadow plugin from 'com.github.johnrengelman.shadow' to 'com.gradleup.shadow'
• Updated Jacoco version to '0.8.12'

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

• Update import using master (deprecated) to clusterManager.

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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