[BUG] CodegenProperties are different instances

The CodegenProperty instances that exist in vars should be the same instances in the other collections, such as requiredVars, optionalVars, etc. If we iterate the vars or allVars to make modifications, we should not also have to iterate the other collections.

You can see this in csharp-netcore using the sample below. The EnumTest class has property OuterEnum. If you compare OuterEnum from vars and allVars, you will see that the vendor extensions are different. A good place to put a break point to see this is the updateNullableTypeProperty method.

generate 
-g csharp-netcore
-i "<path>\openapi-generator\modules\openapi-generator\src\test\resources\3_0\csharp\petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml"
-o <path>\openapi-generator\samples\client\petstore\csharp-netcore\OpenAPIClient-generichost-net6.0
--library generichost
--additional-properties=packageGuid={321C8C3F-0156-40C1-AE42-D59761FB9B6C},useCompareNetObjects=true,disallowAdditionalPropertiesIfNotPresent=false,targetFramework=net6.0,nullableReferenceTypes=false

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Reproduce with the csharp-netcore command and the mentioned petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml spec. Start at updateNullableTypeProperty and compare the OuterEnum CodegenProperty from vars and allVars, then verify that modifications through vars are reflected in requiredVars, optionalVars, and the other collections.