[Compute migrations] Duplicated common types

[AlitzelMendez]

Problem: The SDK generation fails due to duplicated common types in each sub-service, causing duplicated schemas. This issue happens because common types are into each sub-service, leading to duplication.

Proposal: Create a decorator to handle common definitions. This decorator would prevent inlining common types into each sub-service's swagger and instead reference a common location. This approach aims to maintain back compatibility and avoid duplicated schemas

Implementation: Creating a decorator, such as @commonType, to reference common types from a centralized location. This would require manual adjustments to the TypeSpec files to ensure common types are correctly referenced and not duplicated.

Considerations: This will later require manual effort to update TypeSpec files.

Originally, it was mentioned to do this custom for this also applies to other services, not only compute, taking this into consideration, the decorator is not going to be a custom one.