Single type for all validation errors

[Rua]

Changelog:

### Breaking changes

Changes to error reporting:
- `VulkanError` is renamed to `RuntimeError`.
- Added new types `ValidationError` and `VulkanError` (enum of `ValidationError` + `RuntimeError`) to return errors from any function. Some existing functions have been converted to use these types, others will follow later.

After some Discord discussion earlier today, this PR proposes a new way to report validation errors to the user. I've replaced the old error type in compute pipeline creation, as an example to show how it looks in practice. If accepted, this change would be made across the board, but we can do it piecemeal, it doesn't have to be all at once.

The enums that Vulkano currently uses to report errors have many problems:

• Users are very unlikely to want to match on any of the enum variants. These are validation errors, if they happen then they are bugs in the user's code.
• When you unwrap an error, which most people will do, then you only get the debug print, which is far less helpful than the display print.
• They are tedious to create: You have to define a new enum, think of a name, then implement various traits.
• They are tedious to extend: You have to add new variants each time a new error type is added, and then also update the Display implementation to add a friendly message for the user. And again, you have to think of names for all of these variants.
• Their definitions are elsewhere in the code from where the error is triggered, meaning that you have to scroll back and forth whenever you need to change something.
• There are many of them, in the many tens of different types.
• Frankly, I'm fed up with writing enums!

Several years ago, I made a proposal to replace all validation errors in Vulkano with panics: #1546. This was rejected, but it seemed that people were on board with simplifying the error types if Vulkan kept the standard Result + Error error reporting. This implements that now.

[marc0246]

Mucho gracias.