Genericize function-like printer and parser. NFC

Function-like operations are likely to have similar custom syntax, in
particular they all need to print function signature with argument attributes.

Transform function printer and parser so that they can be applied to any
operation with the FunctionLike trait.  Move them to the trait itself.  To
avoid large member functions in the class template, define a concrete base
class for the trait and implement common functionality in it.  This allows
printer and parser to be implemented in a source file without templating.

PiperOrigin-RevId: 260020893