Implement TCGC's Model Types

[iscai-msft]

Language emitters should work to move entirely to TCGC's new ecosystem. I've created a separate issue if people want to first move to the SdkModelType and SdkEnumType. To access these types, you can access and on the type

[joheredi]

The TypeScript emitter already consumes getAllModels which gives us access to SdkModelType and SdkEnumType

autorest.typescript/packages/typespec-ts/src/modular/buildCodeModel.ts

Lines 1876 to 1879 in 8b555e2

	const allModels = getAllModels(dpgContext);
	for (const model of allModels) {
	getType(dpgContext, model.__raw!, { usage: model.usage as UsageFlags });
	}

[lmazuel]

Was discussing with @lirenhe , closing this issue, as the primary purpose was to be sure getAllModels is called, which is the case. Please create a separate issue if you wish to track raw improvements.