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.

SharpYaml v2 のプロジェクト依存関係宣言を特定し、影響を受ける OpenAPI YAML 処理を評価する前に SharpYaml v3 の breaking changes を確認します。依存関係を更新した後、既存のテストスイートを実行します。完了の条件は、SharpYaml v3 が使用され、OpenAPI ドキュメントの YAML 処理の互換性が維持されていることです。