On Windows, the Razor server correctly creates the pid file with
`FileAccess.Write` and `FileOptions.DeleteOnClose`. This requires a share mode
of `FileShare.Write | FileShare.Delete` to open. However, the
`dotnet build-server shutdown` command was opening the file with
`FileShare.Read`. As a result, an `IOException` was being thrown and was not
handled.
This change first opens the file with the appropriate share access and also
properly handles a failure to access or read the contents of the pid file.
Additionally, an integration test was added to test that Razor server shutdown
works as expected.
Fixes#9158.
