VideoBackends:Metal: Log file on failed pipeline compile

The inequality operator is automatically generated by the compiler if `operator==` is defined.

Not doing so produces a warning in clang:
    ISO C++20 considers use of overloaded operator '!=' (with operand types
    'Metal::DepthStencilSelector' and 'Metal::DepthStencilSelector') to be
    ambiguous despite there being a unique best viable function with
    non-reversed arguments

The underlying reason for this warning is an incorrect method signature.

Metal pipelines hold less stuff than Dolphin pipelines, so duplicates will appear