refactor function mesh ci integration tests

[freeznet]

• make function mesh integration tests actually process messages from topic, to test the whole workflow.
• moves all function tests into one integration test action to save CI resources.
• add function sample images for Java, Python and Go.

[freeznet]

@nlu90 @tuteng please help to review this PR if you have time, thanks.

[tuteng]

Set this tag to a variable?

[freeznet]

@tuteng I don't think helm values.yaml support variable in this way, since the values.yaml is a variable collection pass to helm template. But the values can be overwritten by using helm install --set images.zookeeper.tag=2.7.2.

ref: helm/helm#2133