GPU_select originally used GL_SELECT which defined the format for
storing the selection result.
Now this is no longer the case, define our own struct - making the code
easier to follow:
- Avoid having to deal with arrays in both `uint*` and `uint(*)[4]`
multiplying offsets by 4 in some cases & not others.
- No magic numbers for the offsets of depth & selection-ID.
- No need to allocate unused members to match GL_SELECT
(halving the buffer size).
Replace `typedef` with `using` in C++ code.
In the case of `typedef struct SomeName { ... } SomeName;` I removed the
`typedef` altogether, as this is unnecessary in C++. Such cases have been
rewritten to `struct SomeName { ... };`
No functional changes.
This is part of the Vulkan task T68990.
This introduce a new GLQueryPool for managing queries in an
implementation agnostic manner.
This modify the GPU selection query to use this new object.
This also make use of blender::Vector for better code quality.
No real functionnal change.
