`FUNCTION_NAME` source literal doesn't work in class methods

Happens on both v0 and v1.

class MyClass
    sub myMethod()
        print FUNCTION_NAME
    end sub
end class

Transpiles to:

function __MyClass_builder()
    instance = {}
    instance.new = sub()
    end sub

    instance.myMethod = sub()
        print ""      ' <--- actually not sure what it should print... something like "MyClass::myMethod"?
    end sub
    return instance
end function

function MyClass()
    instance = __MyClass_builder()
    instance.new()
    return instance
end function

Start by locating the FUNCTION_NAME handling and the class-method transpilation path, then reproduce the MyClass example from the issue in the relevant compiler test setup. Determine the intended value for a method such as MyClass::myMethod and add coverage showing that the source literal is no longer emitted as an empty string.