Workspace dependencies

[marc0246]

This makes all our dependencies be specified using workspace dependencies, so that they're all in one place and easier to maintain. In particular, it's easy to see at a glance what might need updating or what could be removed, and having multiple versions of the same dependency is less likely to occur. Also, since our own public crates are also workspace dependencies, it's also more convenient to bump their versions since they're all in the same place.

I made examples its own workspace for two reasons:

• It has different and more dependencies than the rest of the repo.
  • It didn't feel right putting dependencies like winit, png, rand, etc. in the root workspace's manifest.
  • The examples need vulkano with default features, while the root crates need it without.
• I'm always forced to remove the examples from the workspace when I checkout a new branch, because otherwise rust-analyzer chokes for a solid minute on each save, rendering my computer unusable in the meantime. A nice side-effect of this change is that since the examples aren't part of the root workspace anymore, rust-analyzer won't check them unless you enter their workspace.

I updated the CI to account for the two workspaces.

[marc0246]

I added a workspace version as well, so that everything is in one place and bumping the version is more streamlined.

[marc0246]

I removed the workspace-level package version again because it's a bit inconvenient in the case when one only needs to bump the patch versions of certain packages.