Make c10::util::get_fully_qualified_type_name() backwards compatible with clang 4 (#31351)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31351
Clang 4 needs the c10:: namespace specifier on fully_qualified_type_name_impl() to work correctly.
Also, let's add an error message for people using clang 3 and earlier, we don't support those compilers anymore but before this PR, they got a crappy message.
ghstack-source-id: 96380163
Test Plan: testinprod
Differential Revision: D19135587
fbshipit-source-id: c206b56240b36e5c207fb2b69c389bb39f1e62aa
