Feature: Add new prop duplicateKeySuffixSeparator for additionalProperties

[nickgros]

Reasons for making this change

This was originally done in #2467, porting to v5 here.

When using additionalProperties and a duplicate property key is added, RJSF automatically changes the duplicate key from e.g. collision to collision-1.

I have a use case where we use additionalProperties, but - is an illegal character for our property keys. I added a FormProp duplicateKeySuffixSeparator to override - with any string.

Couple of questions

• Is there a better/less verbose prop name?
• This could be added to the uiSchema to change the separator per object field. I do not need this for my use case, but it's a potential change that could be made.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[nickgros]

Review: will move to uiSchema, keeping separate from idSeparator because idSeparator implies hierarchy and duplicateKeySuffixSeparator does not).

[heath-freenome]

@nickgros go ahead and merge this!