[GR-70591] [GR-70157] Improve labsjdk one-off process.

[graalvmbot]

Key changes :

• Move labsjdk-builder jobs to labsjdk-ce repository.
• Disable darwin-amd64 jobs.
• Update java --version to include GraalVM version in build data section : ..(build 25+37-LTS-jvmci-25.1-b09)
• Fix --clean-after-build option to effectively cleanup build directory after build process finish.
• Move sensitive data to ci-overlay.
• Add job to create Automated Graal PRs with newly generated snapshots import.
• Appends source and target branches names to labsjdk snapshots names.