Drop mako code and dependency

[ReToCode]

We removed the dependency to mako from Serving in knative/serving#14289.

With this no longer used, the mako go depencendy and all the stub code here in pkg can be dropped.

Work needed

• Check for usage of mako in all knative and knative-extensions repositories prior to deleting it here
• Drop mako golang dependency
• Drop code at "knative.dev/pkg/test/mako/stub-sidecar"
• Find other references (if any) and drop them as well

[ReToCode]

Eventing still has a dependency on the mako-stub. So this task is on hold, until this dependency is removed.

[dprotaso]

cc @pierDipi do you plan on continuing using this stub?

[pierDipi]

I'm not aware of anybody using the performance tests in Eventing, I believe we can remove them and with that the mako usage

[pierDipi]

knative/eventing#7707

[pierDipi]

@Zerpet @ikavgo @mkuratczyk eventing-rabbitmq is using the mako-stub for performance tests, do you still need the mako stub or are you migrating off of it?