Align release artifact naming with Apache incubator conventions

[tuhaihe]

Use base version (without -rcN suffix) for release tarball filename to align with Apache incubator release conventions.

Changes:

• Modified TAR_NAME to use ${VERSION_FILE} instead of ${TAG}
• Tarball filename now follows pattern: apache-cloudberry-backup-${VERSION_FILE}-incubating-src.tar.gz
• Example: apache-cloudberry-backup-2.0.0-incubating-src.tar.gz (instead of apache-cloudberry-backup-2.0.0-incubating-rc1-src.tar.gz)

Benefits:

• Enables direct 'svn mv' to release repository after voting without renaming artifacts
• Aligns with Apache release best practices where RC identifiers are used only for Git tags and voting process, not in final artifact names
• Maintains consistency between tarball filename and extracted directory name

The extracted directory name remains unchanged:
apache-cloudberry-backup-${VERSION_FILE}-incubating/

closes: #ISSUE_Number

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