Add MSBuildProjectDirectory fallback to ProjectDir resolution

[lahma]

fixes #5127

[Copilot]

Pull Request Overview

This pull request addresses issue #5127 by adding a fallback mechanism to resolve the ProjectDir property using the MSBuildProjectDirectory. Key changes include:

• Adding a fallback call to ReadUsingMsBuildTargets if the primary metadata read does not yield a valid ProjectDir.
• Including "MSBuildProjectDirectory" in the requested metadata properties.
• Assigning the ProjectDir from MSBuildProjectDirectory when needed.

Files not reviewed (1)

• Directory.Build.props: Language not supported

Comments suppressed due to low confidence (1)

src/NSwag.Commands/Commands/Generation/AspNetCore/ProjectMetadata.cs:233

• [nitpick] Consider defining 'MSBuildProjectDirectory' as a named constant for better consistency with other metadata key definitions.

"MSBuildProjectDirectory",