build: Add CI remote cache

[janickm]

This pull request enhances the Bazel CI workflow by integrating support for remote caching and Build Event Service (BES) endpoints, improving build performance and observability. Key changes include updating the Bazel setup GitHub Action to accept new remote cache and BES configuration inputs, adjusting cache usage to avoid pollution on pull requests, and propagating the relevant secrets and configuration through the CI workflow jobs.

Bazel Remote Cache & BES Integration:

• Added new required and optional inputs to .github/actions/setup-bazel/action.yml for remote cache endpoints, authentication headers, upload control, and BES endpoints. These inputs allow the action to be configured for remote caching and build event streaming.
• Updated the Bazel setup action to disable local disk cache in CI (favoring remote cache), incremented the cache version to invalidate old caches, and appended new Bazel flags for remote cache and BES configuration in the bazelrc section. [1] [2]

CI Workflow Configuration:

• Propagated the new remote cache and BES configuration inputs into all relevant jobs in .github/workflows/ci.yml, sourcing secrets for endpoints and authentication headers, and conditionally enabling remote cache uploads only for non-pull request events to prevent cache pollution. [1] [2] [3]