Hierarchy building

[radhgupta]

This pull request introduces a new dual constructor pattern for intermediate models in discriminated union hierarchies, ensuring correct instantiation and inheritance when models share discriminator property names with their base models. It adds logic to detect when this pattern is needed, generates the appropriate constructors, and updates constructor initialization to support multi-layer discriminator scenarios. Several new tests are included to validate these changes.

Constructor Pattern Enhancements

• Added a new ConstructorType enum to define different constructor generation strategies, supporting public, private protected, and internal constructors for various use cases.
• Implemented logic in ModelProvider to detect when a model should use the dual constructor pattern (i.e., when it shares a discriminator property name with its base and has derived models).
• Added methods to generate three constructors for intermediate discriminated models: a public constructor (for external use), a private protected constructor (for inheritance), and an internal constructor (for serialization).

Constructor Initialization Logic

• Updated constructor initialization to correctly call the appropriate base constructor, including passing discriminator values when required for intermediate models using the dual constructor pattern.

Testing Multi-Layer Discriminator Hierarchies

• Added comprehensive tests to cover multi-layer discriminator scenarios, including cases with and without discriminator properties at intermediate layers, and verifying correct constructor argument initialization.

Minor Cleanup

• Removed an unused discriminatedKind argument in a test setup for clarity.

Addresses: Azure/azure-sdk-for-net#51958

[github-actions]

No changes needing a change description found.

[JoshLove-msft]

nit: I think we don't need these anymore

[radhgupta]

I am still using it on line 823:
{ var discriminatorParam = new ParameterProvider( DiscriminatorParameterName, $"{DiscriminatorParameterDescription}", new CSharpType(typeof(string))); constructorParameters.Insert(0, discriminatorParam); }

[JoshLove-msft]

Once we adjust BuildConstructorParameters to have a parameter like includeHierarchyDiscriminator and pass that through to GetAllBaseProperties, we shouldn't need it anymore as it will be constructed automatically from the property.

[JoshLove-msft]

Woops we still need to remove these.

[JoshLove-msft]

Looks like the CI is failing

[JoshLove-msft]

Looks great!