libstdc++: Forward arguments for bind_front<f>,bind_back<f>,nttp<f> [PR122022]

libstdc++: Forward arguments for bind_front<f>,bind_back<f>,nttp<f> [PR122022]

This patch fixes a missing forwarding-reference (&&) in _Bind_fn_t::operator()
and lambda returned from not_fn<f>.

The bind_front<f>/bind_back<f> tests were updated to use a structure similar
to r16-3398-g250dd5b5604fbc to cover cases involving zero, one, and many bound
arguments.

	PR libstdc++/122022

libstdc++-v3/ChangeLog:

	* include/std/functional (_Bind_fn_t): Use forwarding reference as
	paremeter.
	(std::not_fn<f>): Use forwarding reference as lambda parameter.
	* testsuite/20_util/function_objects/bind_back/nttp.cc: Rework tests.
	* testsuite/20_util/function_objects/bind_front/nttp.cc: Likewise.
	* testsuite/20_util/function_objects/not_fn/nttp.cc: Add test for
	argument forwarding.