Improve porch package revision save and render time

[ChristopherFry]

To improve the user experience, there's a request for the Config as Data UI to save and render more frequently when a user is actively updating a draft package. Advantages of this includes:

• ensuring the user does not lose all changes to their draft package if their browser happens to crash
• showing the latest validation messages relative to the latest state of the draft package
• showing any resources that are updated with mutators

This can be completed today by updating the PackageRevisionResources resource for the package however this takes several seconds to complete even for simple packages. With this taking several seconds, this will degrade the user experience since the UI will need to wait for the response (to ensure that no resources are updated for instance by a mutator) before allowing the user to make additional changes to the package.

Requesting that performance is researched to see if it can be improved. This can be reproduced with the kpt cli using kpt alpha rpkg push with the kpt-samples echo and ghost packages. Alternative solutions may exist too including dry run.