Add Bazel 8.3.1 support to cloud builder

[nate-selzer]

This PR adds support for Bazel 8.3.1 to the cloud-builders repository.

Changes made:

• Add Docker build step for Bazel 8.3.1
• Add version check for the new version
• Add example tests for 8.3.1 following the existing pattern
• Add image entry in the images section

This follows the same pattern as the existing Bazel versions (5.4.0, 6.4.0, 7.0.1, 7.3.2) and includes all necessary build, test, and deployment steps.

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[nate-selzer]

Hey @nkohlwork, I'm not sure who to tag in here, I see you're the last contributor to this repo, any way you can help me find a reviewer?