libstdc++: Skip redundant assertions in std::array equality [PR106212]

libstdc++: Skip redundant assertions in std::array equality [PR106212]

As PR c++/106212 shows, the Debug Mode checks cause a compilation error
for equality comparisons involving std::array prvalues in constant
expressions. Those Debug Mode checks are redundant when
comparing two std::array objects, because we already know we have a
valid range. We can also avoid the unnecessary step of using
std::__niter_base to do __normal_iterator unwrapping, which isn't needed
because our std::array iterators are just pointers. Using
std::__equal_aux1 instead of std::equal avoids the redundant checks in
std::equal and std::__equal_aux.

libstdc++-v3/ChangeLog:

	PR libstdc++/106212
	* include/std/array (operator==): Use std::__equal_aux1 instead
	of std::equal.
	* testsuite/23_containers/array/comparison_operators/106212.cc:
	New test.