Improve resource info merging

[turbolent]

Work towards #436

Description

Improve how resource info of then/else branches is merged into the parent scope.
Avoid non-deterministic iteration and remove the old pre-allocation of all infos from the branches (BranchesResourceInfo and BranchesResourceInfos)

---

For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[SupunS]

I'm not too familiar with the business logic in this section, but the code-changes look good to me.