RFC: Update to VkFFT 1.3.4 and Vulkano 0.34.1, multiplatform support

[NickKarpowicz]

I worked a bit on updating the library to do a few things that I needed:

• Uses the newest version of VkFFT, after the refactoring into multiple headers
• Uses the newer version of Vulkano (with substantial changes in how buffers are made and command buffers submitted)
• Ability to set newer VkFFT options like DCT and DST mode
• Runs on MacOS and Windows in addition to Linux
• Minimal additional build steps required by including glslang and VkFFT as git submodules
• Dependencies (except for libvulkan and a C/C++ compiler) built via cargo
• Example code that makes it (hopefully) a bit easier to understand the data layout and operations

This did lead to a fairly large number of changes since Vulkano has changed a lot in the past two years, so I apologize for the rather large PR; it turned out more involved than I expected. I tried to be descriptive in the commit messages, but if anything is unclear, please let me know - I'm happy for any feedback you might have!