[libc++] Move some standard tests from test/libcxx (#152982)

This also removes some tests which were redundant, wrong, or never run.
Specifically,

- `libcxx/utilities/meta/stress_tests/*` were never run and are of
questionable usefulness
- `libcxx/utilities/template.bitset/includes.pass.cpp` is completely
redundant and partially incorrect

Also notably,
`libcxx/language.support/support.c.headers/support.c.headers.other/math.lerp.verify.cpp`
has been refactored to only test the standard mandate.

Author: philnik777

libcxx/test/libcxx/language.support/support.c.headers/support.c.headers.other/math.lerp.verify.cpp

@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <math.h>
+
+// [support.c.headers.other]/1
+//   ... except for the functions described in [sf.cmath], the
+//   std::lerp function overloads ([c.math.lerp]) ...
+
+#include <cassert>
+#include <math.h>
+
+template <class = int>
+int lerp(float, float, float) {
+  return 32;
+}
+
+template <class = int>
+int lerp(double, double, double) {
+  return 32;
+}
+
+template <class = int>
+int lerp(long double, long double, long double) {
+  return 32;
+}
+
+int main(int, char**) {
+  assert(lerp(0.f, 0.f, 0.f) == 32);
+  assert(lerp(0., 0., 0.) == 32);
+  assert(lerp(0.l, 0.l, 0.l) == 32);
+
+  return 0;
+}

libcxx/test/libcxx/utilities/meta/stress_tests/stress_test_is_same.sh.cpp

@@ -6,7 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// REQUIRES: target={{.+}}-aix{{.*}}
 // ADDITIONAL_COMPILE_FLAGS: -fvisibility-inlines-hidden
 
 // When there is a weak hidden symbol in user code and a strong definition