Replaced defaultValue with ??

[jfayot]

Description

• Deprecated defaultValue function, replaced by nullish coalescing operator.
• Deprecated defaultValue.EMPTY_OBJECT, replaced by Frozen.EMPTY_OBJECT.
• Added Frozen namespace with EMPTY_ARRAY and EMPTY_OBJECT frozen values and associated documentation.
• Replaced [] by DefaultValues.EMPTY_ARRAY only where appropriate.
• Updated coding guide.

Issue number and link

Fixes #11674

Testing plan

• All specs still pass.
• Functionally, everything should be the same, so primarily review the files themselves.

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @jfayot!

✅ We can confirm we have a CLA on file for you.

[jjspace]

Thanks for the PR @jfayot! Overall the code changes all seem good to me, just a couple minor comments.

Would you also be able to post a comment with the steps/process you took to do this? I suspect that anyone that was using these functions (like some of our other internal libraries) is using them everywhere and need a large PR like this. It would greatly benefit them if you already found a process that works well

[jfayot]

@jjspace, I think it is ready for another review.

I've created a repo in which you will find the migration scripts. It has some limitations, but still could be useful and be adapted for specific use cases. Off course it can be shared with the community.

[jfayot]

Hi @jjspace ! Will you have some time to dedicate on reviewing final changes for this PR ?

[jjspace]

Thanks for the changes and comments @jfayot. This is very close, just some last organizational comments

[jfayot]

@jjspace this should be ready for another review!

The migration scripts have been updated accordingly...

[jjspace]

LGTM, really happy to get this in! Thanks for all the work on this @jfayot!