Reverts llvm/llvm-project#148613
Considering object argument conversion qualifications perfect leads to
situations where we prefer a non-template const qualified function over
a non-qualified template function, which is very wrong indeed.
I explored solutions to work around that, but instead, we might want to
go the GCC road and prefer the friend overload in the #147374 example,
as this seems a lot more consistent and reliable
(cherry picked from commit 28e1e7e1b4b059a2e42f68061475cddb4ad0a6a3)
7ac3c62282