Normalize capitalization for types while port forwarding

[BlenderDude]

Description
Currently, if --port-forward is used, skaffold will create automated port forwards for resources that are not defined in the portForward field. This works great, but sometimes there are issues with capitalization. For example, I was recently working on a project where the type of the service resource was understood to be service by skaffold, but in the portForward section of the skaffold.yaml, I had set the Type to Service. These were interpreted as two different port forwarding configurations and leads to unintentional duplication on the same resource.

My solution to this was to normalize the capitalization when calculating the key for the portForwardEntry. This makes it such that resources of the same type, but different capitalization, will be treated the same. Ex. service/my-api-service and Service/my-api-service will be treated the same.

A unit test has been added to support this.

[codecov]

Codecov Report

Merging #3803 into master will increase coverage by 0.01%.
The diff coverage is 100%.

Impacted Files	Coverage Δ
...ffold/kubernetes/portforward/port_forward_entry.go	100% <100%> (ø)	⬆️
...affold/kubernetes/portforward/kubectl_forwarder.go	68.29% <0%> (+2.43%)	⬆️