[csharp-netcore] Remove use of dynamic type and optimize reference (!5206) · Merge requests · OpenAPI Tools / openapi-generator

Created by: shibayan

Remove unnecessary use of dynamic
- In C#, dynamic and object have the same type, so there is no need to differentiate code with sync or async
Optimize package reference according to options
- CompareNETObjects is only needed when useCompareNetObjects is specified
- System.ComponentModel.Annotations is only needed when validatable is specified

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