[v3-3-test] Speed up lang-SDK k8s test by building Go/Java natively in CI (#69411)

[jason810496]

• Speed up lang-SDK k8s test by building Go/Java natively in CI

The Multi-Lang KubernetesExecutor system test builds a Go bundle and a Java jar inside throwaway toolchain containers. On a dev host the module, Gradle-distribution and dependency caches persist between runs, but CI runners are ephemeral and nothing cached them, so every scheduled run re-pulled the golang/temurin images and re-downloaded the Gradle distribution and all dependencies — adding roughly ten minutes to each of the six KubernetesExecutor variants that run the test.

Build the artifacts with the host toolchain in CI instead, provisioned and cached through actions/setup-go and actions/setup-java, so the toolchain image pulls and cold dependency downloads no longer happen on every run. Local runs keep the containerised build so a dev host still needs neither Go nor a JDK installed.

• Centralize lang-SDK JDK version and add a bustable cache key in CI

Follow-ups to the native lang-SDK build:

• Move the JDK version (17) into a JAVA_SDK_VERSION breeze constant and surface it as the java-sdk-version selective-checks / build-info output, so the k8s workflow reads it instead of hardcoding the version in YAML.
• Restore the Go module/build and Gradle caches with an explicit actions/cache keyed on a "-v1-" salt rather than the setup-* built-in caching, giving an in-repo knob to force-invalidate a poisoned cache (bump the salt) without waiting for a dependency change to rotate it. (cherry picked from commit 673183b)