Fix voicebank error check

[maiko3tattun]

Improvements:

• When loading voicebanks, setting an error and "oto.IsValid = false" for aliases if wav does not exist.
• Improved singer's error report:
  sample rate, channels, and alias duplicates are now reported.
  

[maiko3tattun]

I'll have to modify the tests...

[maiko3tattun]

I had to write dirty code to pass the tests ; ;

[stakira]

It's wasteful to check for every oto line. It would be better to parse all lines first, then check files.

[maiko3tattun]

I updated it.

[stakira]

Alternative, conversion can be done like how non-wav files are handled. See

OpenUtau/OpenUtau.Core/Classic/VoicebankFiles.cs

Lines 83 to 93 in 05076e4

	if (Path.GetExtension(source) == ".wav") {
	Log.Verbose($"Copy {source} to {dest}");
	File.Copy(source, dest);
	return;
	}
	Log.Verbose($"Decode {source} to {dest}");
	using (var outputStream = new FileStream(dest, FileMode.Create)) {
	using (var waveStream = Core.Format.Wave.OpenFile(source)) {
	WaveFileWriter.WriteWavFileToStream(outputStream, waveStream);
	}
	}

[maiko3tattun]

This is an error report and should be reported down to the smallest detail.
In fact, the current worldline will not play correctly if the sample rate is incorrect. There is also a possibility that voicebanks created by OU could be distributed and used by OG UTAU.

[maiko3tattun]

Minor errors in error reports are separated as information.
This is because information such as missing character.yaml is misinterpreted as if it were a serious error.

Currently, stereo files that are supported by worldline are reported as information, not 44100 Hz files that are not supported by worldline are reported as errors.
It is true that worldline should support a variety of sample rates, but that is a discussion for another place.