Right now, flutter_tester --enable-impeller is dynamically resolving libvk_swiftshader from the dyld path, but we should be able to link it statically.

When I worked on this I tried static linking initially and had some trouble, so I just did some dynamic linking as we do in other test harnesses. It would be easier for customers downstream (e.g. the framework) if it's linked statically.

/cc @chinmaygarde @bdero @jonahwilliams