Add code paths to compile and execute UTF-8 buffers directly

[AnsisMalins]

This change avoids allocating large UTF-16 strings when the source material is in UTF-8, which is approximately 100% of the Web. The specific use case for myself is obtaining a native pointer to a buffer from the Unity game engine and passing it straight through to ClearScript's native side. When loading code files using managed code, a single buffer the size of the largest code file can be reused.

I'll add tests and more overloads after you indicate that you would accept this at all.

The T4 is generating lots of additional empty lines. Afacit, that is correct given the template code, but then why weren't they there in the first place.