Extend IR model and Composer API

Composer API

Extend the composer API and IR to improve flexibility and support more C++ language features, in particular

• constexpr, [[attributes]], static on functions / methods
• manually specified function parameter lists
• default and delete keywords for ctors (and dtors)
• static class member variables
• separate declarations and definitions for (static) class member variables
• Allow defining constructors non-inline
• Add a signature of .init() to the constructor builder that takes a dictionary of member-initializers
• Add a class composer method for destructors
• Also, it should be possible to expose kernels by adding their declaration to the header file, and to generate inline kernel definitions into the header.

IR

• Extend the IR to support the above concepts