Adds free form model generation in python-experimental

Created by: spacether

If a free form object schema has validations I think that we should generate it as a model

• I think that we should do this to allow another composed schema to oneOf include an object schema with validations
• In the current master branch, those validations are omitted because there will not be a model to contain the validations

If a free form schema is used as an interface schema (another schema allOf includes it) I think that we should generate the interface as a model

• Note: this is another way of implementing interface models which is similar to https://github.com/OpenAPITools/openapi-generator/pull/6849 but doesn't require our users to know about a specific vendor extension.

If merged, this will resolve https://github.com/OpenAPITools/openapi-generator/issues/7361 for python-experimental only

• Tests added for these free form schema use cases

How this change was made:

• unaliasSchema is changed into a public method in each generator
• when generating models, if we are examining a FreeFormObject, we create a schema ref to it and see if unaliasSchema preserves the ref(meaning the model will be generated) or it unaliases the schema (meaning the model won't be generated)
• the method hasValidation is added to codegenModel to return a boolean saying if there is validation in the root level of the component schema that we are examining. This is needed to check if arrayModels have validations in all generators that make arraymodels. This is also needed in python-experimental to produce FreeFormObject models with validation.

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