Provide a way to hide port-forwards in the Tilt UI

When I am developing APIs that are used internally (e.g. REST or gRPC), I need to create port-forwards to things that do not display a webpage, but are used by other applications. In these situations, I want to add a Link to a k8s_resource referencing my other application that uses an API, and not show an HTTP address to the API endpoint itself in the Tilt UI.

One example is when I am running a GraphQL Playground separately that connects to a graphql API. I do not want to show the API endpoint as an HTTP URL in the Tilt UI. Instead, I can add a Link to the GraphQL Playground website where I can make interactive calls to the API using my port-forward.

Unfortunately, there does not seem to be any option to create a port-forward and completely hide or make non-clickable the hyperlink in the UI.
https://github.com/tilt-dev/tilt/blob/d79b05e6a6f667e0a34599878a36394590fc8932/pkg/model/manifest.go#L448-L450

This has been pretty confusing for my users, since they get a set of links like http://localhost:8080 that just show error codes if clicked. Right now I am using the option name="dontclickme", but this is a silly workaround.

Start with the k8s_resource port-forward fields in pkg/model/manifest.go around lines 448-450, then trace how those values are rendered in the Tilt UI. Done means a port-forward can be created without showing a clickable HTTP endpoint, while an explicit Link to another application remains visible.