cm, wit/bindgen: implement flags types with > 64 labels

[ydnar]

Related to WebAssembly/component-model#370, the Go code generation for flags types currently supports flags with <= 64 labels. This is consistent with wit-bindgen (for C and possibly other languages) code generation.

Tasks

• Implement flags with > 64 labels, with appropriate bindings generation for flags types that won’t fit in a single integer type.
• Implement CABI lift and lower code for flags types larger than uint64.