Fixes intermittent issues in model renaming.

[andrueastman]

This PR fixes microsoftgraph/msgraph-sdk-dotnet#2084

After changes made in #3107 involved the CodeType sharing the name with the TypeDefinition property to limit unnecessary string copies. This however led to indeterministic renaming of model types as renaming a TypeDefinition instance through the parameter type or discriminator mapping would lead to indeterministic results depending on which was processed first and sometimes fail to check for conflicts after renaming.
An example include renaming microsoft.graph.directory to microsoft.graph.directoryObject (which already exists rather than resolving the renaming conflict) when the TypeDefinition when encountered through the discriminator mapping of the base rather than as child element of the microsoft.graph namespace.

This PR therefore eliminates other points of TypeDefinition/CodeType renaming(as multiple string copies are no longer held) by dropping functions that looked up the TypeDefinition/CodeType name indirectly through the

• Discriminator mappings
• Code using declarations
• Parameter types

[sonarqubecloud]

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90.0% Coverage
0.0% Duplication

[baywet]

Thanks for fixing that. Even less work to do since we're already renaming the definitions (class/interface/enum)