Update SharpYaml dependency to v3.x

Is your feature request related to a problem? Please describe.

OpenAPI.NET currently depends on SharpYaml v2. In my project, I use OpenAPI.NET to process OpenAPI documents and also need to read additional YAML-based configuration files.

SharpYaml v3 is a major redesign that introduces breaking changes compared to v2. Since OpenAPI.NET brings SharpYaml v2 as a dependency, I am currently forced to continue developing against the older SharpYaml API and plan a future migration.

Describe the solution you'd like

I would like OpenAPI.NET to update its SharpYaml dependency from v2 to the latest v3 release.

Describe alternatives you've considered

• Continuing to use SharpYaml v2 in my own code and migrating later.
• Isolating YAML processing behind an abstraction layer to minimize the impact of a future migration.
• Using a different YAML library for application-specific configuration files.

While these approaches are possible, they add complexity that could be avoided if OpenAPI.NET adopted SharpYaml v3 directly.

定位项目中对 SharpYaml v2 的依赖声明，并在评估受影响的 OpenAPI YAML 处理之前，检查 SharpYaml v3 的 breaking changes。更新依赖后运行现有测试套件；完成的标准是使用 SharpYaml v3，并且 OpenAPI 文档的 YAML 处理仍保持兼容。