Look at ~10 minute backend system tests to find performance improvements

[linear-code]

system-tests-backend.yml is a GitHub Actions workflow that runs end-to-end backend system tests against Spring Boot, WebFlux, OpenTelemetry, and console sample apps.

The workflow explicitly strips every Android module from the build via a sed step before running: Android code plays no role in these tests. The matrix is large (20+ sample/agent combinations), making it one of the more expensive CI workflows in the repo.

We should update its config so that Android-only changes no longer trigger the tests.

[linear-code]

JAVA-519