[cuvs] Use official libcuvs nightlies for snapshots

[brianseeders]

We are now using libcuvs nightlies to build cuvs-java and storing everything in GCS. This building/packaging happens in a separate repo.

• Move cuvs-java version to build-tools-internal/version.properties, since it is referenced from multiple places
• For CI, download and configure libcuvs based on the requested version of cuvs-java in build-tools-internal/version.properties
• Dynamically switch to our GCS bucket for SNAPSHOT versions, use official Maven for actual releases
• Update the daily update script to account for all of the changes
• Make it possible to use the update pipeline to also update to official release versions
• Locally, you can also run source .buildkite/scripts/cuvs-snapshot/configure.sh to set up libcuv

This branch currently has cuvs 25.10.0 for this merge, but it will automatically be updated with 25.12.0 nightlies going forward.

[elasticsearchmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[ChrisHegarty]

Thanks Brian, LGTM

[brianseeders]

💚 All backports created successfully

Status	Branch	Result
✅	9.2

Questions ?

Please refer to the Backport tool documentation