fix: FFI > Create managed binary data

[tienvx]

FFI: Change from unmanaged data to managed data

For #371

[Lewiscowles1986]

Would appreciate any links you have on this, but I think it should help to prevent memory leaks if managed is the same type of [memory] management I'd think of. Interesting that it's not the default as past ffi, it's in PHP and should work as PHP would expect (managed)

[tienvx]

Here is the link about $owned parameter of FFI::new():

https://www.php.net/manual/en/ffi.new.php#refsect1-ffi.new-parameters

owned: Whether to create owned (i.e. managed) or unmanaged data. Managed data lives together with the returned FFI\CData object, and is released when the last reference to that object is released by regular PHP reference counting or GC. Unmanaged data should be released by calling FFI::free(), when no longer needed.

What I did there is to keep the $cData object alive, by creating object of type BinaryData as a property of object of type Binary, which live long enough throughout the binary's consumer example.