Generics support on various code points

[moznion]

Support the generics syntax in the following syntaxes/notations:

• generic types on function invocation like foo[int64](123)
• generic parameter names on function receiver like func (s MyStruct[T])
• generic parameter names on function return values like func foo[T struct]() MyStruct[T]
• generic type parameters on interface declaration like type MyInterface[T any] interface {}

This patch also introduces TypeParameterNames which is an alias of []string to represent the generic parameter names, e.g. T.
And this patch makes it supports the generics union types.