Also rename the test so it actually runs.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/102270
	* include/std/tuple (_Tuple_impl): Add constexpr to constructor
	missed in previous patch.
	* testsuite/20_util/tuple/cons/102270.C: Moved to...
	* testsuite/20_util/tuple/cons/102270.cc: ...here.
	* testsuite/util/testsuite_allocator.h (SimpleAllocator): Add
	constexpr to constructor so it can be used for C++20 tests.

Tested powerpc64le-linux. Committed to trunk.

git mailpatch 42eff613d0c10f88dc7a44b14981876401a09981