[Improve][CI] Optimize changes job engine module calculation

[davidzollo]

Purpose

The changes workflow job currently spends most of its time in Maven dependency tree resolution when a change only touches engine files. Existing samples show this path can take 7-9 minutes even though engine changes already route broad downstream CI through engine=true.

Changes

• Add a fast path for pure engine changes in Make unit test modules.
• Add the same fast path in Make integration test modules when no connector or engine-e2e module changed.
• Preserve the existing fixed engine smoke module outputs so downstream conditions remain compatible.

Validation

• git diff --check
• Ruby YAML parse for .github/workflows/backend.yml
• Engine helper mapping check for connector-seatunnel-e2e-base and connector-console-seatunnel-e2e
• Bash simulation for engine-only and mixed engine+connector routing
• ./mvnw spotless:apply -nsu -Dmaven.gitcommitid.skip=true
• ./mvnw -q -DskipTests verify -Dskip.ui=true -Dlicense.skipAddThirdParty=true -nsu -Dmaven.gitcommitid.skip=true -T 3C