H-2303: Overhaul merge logic for entity types

[TimDiekmann]

🌟 What is the purpose of this PR?

Quite a few issues were detected in the type system package. This fixes a few of them.

🔍 What does this change?

• Properly implement merging entity types (properties, required, links)
• Fix a deserializing issue for links
• Don't allow 0 in maxItems
• Make ordered in links optional (it's deprecated)
• Tests for merging links were added

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• [x] does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• [x] are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• [x] do not affect the execution graph