This provides updates to
Pre C++20 [class.mfct]p2:
A member function may be defined (8.4) in its class definition, in which case it is an inline member function (7.1.2)
Post C++20 [class.mfct]p1:
If a member function is attached to the global module and is defined in its class definition, it is inline.
A function can be defined in a friend declaration of a class . . . . Such a function is implicitly inline.
Post C++20 [class.friend]p7
Such a function is implicitly an inline function if it is attached to the global module.
We add the output of implicit-inline to the TextNodeDumper, and amend
a couple of existing tests to account for this, plus add tests for the
cases covered above.