Remove outdated code from revision, etc dealing with services

[vagababov]

/lint
part of #1997

Proposed Changes

• Deletes the code that is no longer used.
• Moves some constants around

/cc @mattmoor

[knative-prow-robot]

@vagababov: 0 warnings.

In response to this:

/lint
part of #1997

Proposed Changes

• Deletes the code that is no longer used.
• Moves some constants around

/cc @mattmoor

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[mattmoor]

/lgtm
/approve

Red lines are the best lines. 🎉

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mattmoor, vagababov

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• pkg/activator/OWNERS [mattmoor,vagababov]
• pkg/apis/autoscaling/OWNERS [mattmoor]
• pkg/apis/networking/OWNERS [mattmoor,vagababov]
• pkg/reconciler/OWNERS [mattmoor,vagababov]

Approvers can indicate their approval by writing /approve in a comment
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[knative-metrics-robot]

The following is the coverage report on pkg/.
Say /test pull-knative-serving-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/autoscaling/v1alpha1/pa_validation.go	75.6%	75.0%	-0.6
pkg/reconciler/autoscaling/hpa/hpa.go	Do not exist	93.8%
pkg/reconciler/autoscaling/kpa/kpa.go	Do not exist	91.4%
pkg/reconciler/autoscaling/kpa/resources/service.go	Do not exist	100.0%
pkg/reconciler/revision/resources/kpa.go	Do not exist	100.0%
pkg/reconciler/revision/resources/names/names.go	Do not exist	100.0%
pkg/reconciler/route/resources/service.go	Do not exist	100.0%