[clang][ItaniumMangle] Mangle friend function templates with a constr… (#110247)

…aint that depends on a template parameter from an enclosing template as
members of the enclosing class.

Such function templates should be considered member-like constrained
friends per [temp.friend]p9 and
https://github.com/itanium-cxx-abi/cxx-abi/issues/24#issuecomment-934977198).

GitOrigin-RevId: 147558e31c2b8d2986fc13cf6f9e2bf6a120f2e6