[test] Define _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST in msvc_stdlib_force_include.hpp

...so the tests under test/std/utilities/any continue to
compile with MSVC's standard library.

While we're here, let's test >C++17 features when _HAS_CXX20.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@351991 91177308-0d34-0410-b5e6-96231b3b80d8
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