Near-full support for VK_KHR_synchronization2

[Rua]

Changelog:

### Breaking changes
Changes to `PipelineStages`:
- The `transfer` flag has been renamed to `all_transfer`.

Changes to `SubpassDependency`, `MemoryBarrier`, `BufferMemoryBarrier`, `ImageMemoryBarrier`:
- Fields that start with `source_` have been renamed to `src_`.
- Fields that start with `destination_` have been renamed to `dst_`.

Changes to the `set_event` command:
- This command now takes a `DependencyInfo` instead of `PipelineStages`, to enable use of the `vkCmdSetEvent2` version.

### Additions
- Added support for all remaining `PipelineStages` and `AccessFlags`, including those from the `synchronization2` feature.
- Added support for `synchronization2` to the `set_event`, `reset_event` and `write_timestamp` commands, and to `SubpassDependency` when creating a render pass.
- Added the `wait_events` command to `SyncCommandBufferBuilder` and `UnsafeCommandBufferBuilder`.

Almost all of this extension is now implemented as far as possible. The only remaining parts are those that deal with device groups, which Vulkano doesn't have any support for yet anyway.

[AustinJ235]

Great work!