Adds codegenParameter.schema to allow referenced schemas in parameters

[spacether]

Adds codegenParameter.schema to allow referenced schemas in parameters
This allows referenced schemas in request parameters as #10927 requests.
In the future whole parameters may be referenced, so adding a class property which stores a schema codegenProperty allows us to:

• store when there is a schema for a Parameter
• tell when that schema is referenced to a component
• will allow us to tell the difference in the future between a referenced Parameter and a referenced parameter schema
  • right now for a single schema or content schema, those schema's properties like isMap are stored on codegenParameter.
  • that is an unclear way to do it because let's say the parameter references parameter definition in components/parameters as a ref property in codegenParameter. Does that ref property mean that the Parameter is referenced or the parameter schema is referenced?

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