New image acquiring API, swapchain release fix

[kvark]

The old logic was consuming the swapchain when it was passed as the old swapchain. This was incorrect, since Vulkan apps are still expected to destroy those swapchains.

The PR also adds GFX_METAL_ACQUIRING=wait|oldest command line. The benefit of wait at this moment is a simpler acquire implementation and proper error codes for it, unlike the oldest one (to be addressed).

Also, -vulkan_disable_occlusion_queries are back since apparently Dota2 requires more queries in total than our global query buffer can fit.

[bors[bot]]

Build failed

• continuous-integration/travis-ci/push

[msiglreith]

bors r+

[bors[bot]]

Build succeeded

• continuous-integration/travis-ci/push
• continuous-integration/appveyor/branch