feat(codegen,types): SetRelation on expanded types (#3477)

## What

On expanded relations, mutate type using SetRelation, an alias for SetRequired with SetNonNullable.

## Why

Simplifies implementation in client code.

## How

* Export SetRelation type util
* Update codegen template

Extra scope:

* Improve codegen error handling when processing x-expanded-relations
* Add `eager` sub-categorization to x-expanded-relations to highlight relations that are loaded using TypeORM eager.

.changeset/quiet-spiders-join.md

@@ -0,0 +1,6 @@
+---
+"@medusajs/openapi-typescript-codegen": minor
+"@medusajs/client-types": minor
+---
+
+feat(codegen,types): SetRelation on expanded types