[clang] Exclude non-template classes when checking if constraint refers to...

[clang] Exclude non-template classes when checking if constraint refers to containing template arguments (#74265)

When checking if the constraint uses any enclosing template parameters
for [temp.friend]p9, if a containing record is used as argument, we
assume that the constraint depends on enclosing template parameters
without checking if the record is templated. The reproducer from the bug
is included as a test case.

Fixes #71595