Fix missing "Optional parameter before required" deprecation on union null type

The check would only work for the ?type syntax, but not type|null. Switch to a
check during type compilat

Fix missing "Optional parameter before required" deprecation on union null type

The check would only work for the ?type syntax, but not type|null. Switch to a
check during type compilation instead.

Fixes GH-11488
Closes GH-11497

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