Generate TryInsert methods for C# modules

[joshua-spacetime]

C# doesn't generate TryInsert methods. See module-test-cs.

[gefjon]

This is part of the intended design (for what that's worth; it's totally fair to criticize the intended design). My belief is that try_* methods are only necessary in Rust, where panicking is distinct from returning an error; in C#, both are encompassed by throwing an exception, so you only need one method.