fix(ci): limit JVM heap for CI containers and replace pack with docker build

[shreemaan-abhishek]

Summary

• Limit JVM heap sizes for Kafka, Zookeeper, SkyWalking, RocketMQ, GraphQL demo, and Petstore CI containers to reduce memory pressure
• Replace Cloud Native Buildpacks (pack) with standard docker build for openfunction test images, eliminating the pack binary download and simplifying the build process
• Add Dockerfiles and Go entrypoints for test-uri, test-body, and test-header function images

Test plan

• JVM heap limits added to all Java-based CI services
• Dockerfiles build equivalent images to the previous buildpack approach
• build-function-image.sh uses docker build instead of pack