Add tests

[patrickroberts]

Need

• noexcept correctness
• constexpr evaluation
• validate that SBO is used under correct conditions
• Non-trivial value_type (preferably one that allocates)

[patrickroberts]

Also want to use [[clang::lifetimebound]] attribute on range parameter of any_view constructor and add clang-specific compile-fail tests to demonstrate the borrow-checking safety it enables.