Cleanup nonportable behavior in tests for std::any

Fixes MS issues 63, 64, and 65.

test/std/utilities/any/any.class/any.cons/move.pass.cpp:
* "Moves are always destructive" is not a portable assumption; check with LIBCPP_ASSERT.

test/std/utilities/any/any.class/any.cons/value.pass.cpp:
* The standard does not forbid initializing std::any from any pointer-to-function type. Remove the non-conforming "DecayTag" test.

test/std/utilities/any/any.class/any.modifiers/swap.pass.cpp:
* Self-swap is not specified to perform no moves; check with LIBCPP_ASSERT.

Differential Revision: https://reviews.llvm.org/D26007

llvm-svn: 285234