Kickstart UI: add a MappedStep class (refactor)

[swalner-vmware]

Bug description
We have introduced "step mapping" into the current code base, but much of the code (in steps that use "step mapping") could be collected into a base class to avoid repetition. Our current base step class already has much in it, and we have at least one step subclass (WcpRedirect) that doesn't use the step mapping, so it would make sense to introduce a MappedStep class to serve as a base class to most of our current steps. This would also be a good class to include in a library.

Affected product area (please put an X in all that apply)

• APIs
• Addons
• CLI
• Docs
• IAM
• Installation
• Plugin
• Security
• Test and Release
• User Experience

Expected behavior

Steps to reproduce the bug

Version (include the SHA if the version is not obvious)

Environment where the bug was observed (cloud, OS, etc)

Relevant Debug Output (Logs, manifests, etc)