libstdc++: Disable std::formatter::set_debug_format [PR112832]

All set_debug_format member functions should be guarded by the
__cpp_lib_formatting_ranges macro (which is not defined yet).

libstdc++-v3/ChangeLog:

	PR libstdc++/112832
	* include/std/format (formatter::set_debug_format): Ensure this
	member is defined conditionally for all specializations.
	* testsuite/std/format/formatter/112832.cc: New test.

(cherry picked from commit 3cd73543)