[Bug]: Honor `loadOnDemand` in `ResourceSet.Resource(...)`

[samatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the EcoreNetto
• I have searched open and closed issues to ensure it has not already been reported

Description

• Summary: ResourceSet.Resource(Uri uri, bool loadOnDemand) ignores loadOnDemand: it only searches existing resources and returns null when not found, never creating/loading on demand. The parameter is part of the contract but has no effect.
• Affected files: ECoreNetto/Resource/ResourceSet.cs:146-162
• Proposed solution: When loadOnDemand is true and no matching resource exists, create and load it (mirroring the demand-load already done in Resource.GetEObject).
• Acceptance criteria:
  • With loadOnDemand: true, a not-yet-loaded resource is created and loaded.
  • With loadOnDemand: false, behavior is unchanged.
  • Tests cover both paths.