Unified release workflow for shaded and thin JARs

[gopalldb]

Summary

This PR simplifies the release process by publishing both shaded and thin JARs in a single unified workflow, replacing the multi-module approach with a cleaner single-module solution.

Changes

pom.xml

• Added build-helper-maven-plugin to attach unshaded JAR with -thin classifier before shading
• This creates databricks-jdbc-{version}-thin.jar automatically during build

.github/workflows/release.yml

• Merged release and release-thin workflows into one
• Publishes both artifacts to Maven Central in sequence:
  1. Shaded JAR: com.databricks:databricks-jdbc (main artifact)
  2. Thin JAR: com.databricks:databricks-jdbc-thin (with thin_public_pom.xml)

.github/workflows/release-thin.yml

• Deleted (no longer needed - functionality merged into release.yml)

Benefits

✅ Single workflow - Both JARs published in one GitHub Actions run
✅ Minimal changes - Only 3 files modified, no code refactoring
✅ Backward compatible - Existing users unaffected (shaded JAR remains main artifact)
✅ Simple maintenance - Single module, no parent/child POM complexity
✅ Clean build - mvn package creates both JARs automatically

Build Output

target/databricks-jdbc-3.0.1.jar       (37MB shaded uber JAR)
target/databricks-jdbc-3.0.1-thin.jar  (2.4MB thin JAR, driver classes only)

Testing

• ✅ Local build successful
• ✅ Both JARs created with correct content
• ✅ Thin JAR verified: contains driver classes, no shaded dependencies

Replaces

This is a simpler alternative to PR databricks#1042 (multi-module approach), providing the same functionality with less complexity.

NO_CHANGELOG=true - Infrastructure change, no user-facing functionality changes