Fix TraceParserGen to generate meaningful parser for WPF

[oatkins]

This attempts to resolve https://github.com/microsoft/perfview/issues/1351 and supports creating a parser for the Microsoft-Windows-WPF provider from the manifest at C:\Windows\Microsoft.NET\Framework\v4.0.30319\WPF\wpf-etw.man.

See also https://github.com/microsoft/perfview/issues/554.

Addresses various issues with the generated provider:

• Enum should not be normalized it if's already PascalCase, so the normalizing logic is skipped if no "_" is present in a field name.
• RegisterTemplate() seems not to exist; source.RegisterEventTemplate is apparently what was intended.
• Task GUID constants were previously referenced but not generated.
• Template class names were incorrectly referenced.

[ghost]

All CLA requirements met.

[oatkins]

See also #950 - need to make sure the problems resolved there are not reintroduced here.