Remove the resources of the older version, if a new version of knative is installed.

[houshengbo]

Currently, when we install the operator of an new version, in a cluster, where there is an older version operator, the resources of knative serving will be overwritten or brand-new installed, depending on whether the resource exists or not.

However, if the new version of knative serving remove resources compared to the old version, the operator should remove those resources.

Since all the resources are labeled with "serving.knative.dev/release="<Version>", we can use the version number to find all the resources at the older version.

[k4leung4]

Are there scenarios where a resource is in a transition state, supported and not created in a given version?

for example

• resource created, supported in version A
• resource not created, marked as deprecated but still supported in version B
• resource no longer support supported in version C