[Feature Request] Stop `docfx metadata` command immediately when restore failed

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

`docfx metadata` command failed to restore project.
It show error messages only to console. But processing continues.

It's not counted as error. So it may return ExitCode: 0
It might be better to raise error and stop processing.

https://github.com/dotnet/docfx/blob/8b43a7ab7719a93cbd2c73e7d629a079042949bb/src/Docfx.Dotnet/DotnetApiCatalog.Compile.cs#L153-L157

**Describe the solution you'd like**
When restore operation failed. stop processing and show errors.