REST UI has been creating 'method' granularity configuration: provide update path to automatically convert to 'resource' granularity where possible

Problem/Motivation

1. #2721595: Simplify REST configuration introduced 'resource' granularity configuration. It shipped with 8.2.0. 8.3.0 was released last week. Yet REST UI still does not yet support this.
2. #2831716: REST UI does not support "resource" granularity updates REST UI to support 'resource' granularity.
3. But what about all the REST resource config that was created in the mean time?

Proposed resolution

#2721595: Simplify REST configuration provided an update path, which did this:

// If each method has the same formats and the same authentication
// providers configured, convert it to 'granularity: resource', which has
// a simpler/less verbose configuration.

IOW: if you have the same formats and the same authentication configured for every method that you have enabled in your 'method' granularity REST resource configuration… then it is converted to 'resource' granularity. It expresses the same, and is not as needlessly complex.

We can simply reuse that same update path in the REST UI module!

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes