Remove generated 'As<I>()' methods for static types

[Sergio0694]

This PR removes the generated As<I>() methods on static RCW types. This method is:

• Unnecessary, now that ActivationFactory is public
• Only works with either [ComImport] types, or via IDIC
• It doesn't exist on non-static RCW types, which is not consistent (eg. Win2D uses that)

Devs should just use ActivationFactory directly, which also exposes new high perf methods.

[hez2010]

Isn't it an ABI breaking change? I don't think it's acceptable though as all existing apps including WinRT component libraries will stop working. Maybe you can put this under yet another feature flag to make it an opt-in feature. Keeping the As<I>() is also good for developer experience (string cannot be replaced automatically when doing refactor on namespace/type names).

[Sergio0694]

Closing this too, moving to 3.0.