[Request] Add support for custom resolve of MSAA buffers

[Froyok]

While love supports MSAA textures, it automatically resolves them when they are binded to a shader. This is a problem in my case as I would like to resolve them myself instead. The main reason being that I render HDR content and would need to tonemap the samples by hand before combining them.

For concrete examples, see the following blog posts:

• https://therealmjp.github.io/posts/msaa-overview/
• https://therealmjp.github.io/posts/msaa-resolve-filters/

Custom resolve could also open the door to more advanced tricks as well.

I personally don't a preferred way to achieve this.

This could be either an boolean option in when creating the texture/canvas to specify that it shouldn't be automatically resolved, or more implicit depending where it is binded (for example: binding in a compute shader wouldn't trigger the automatic resolve). I imagine ideally an explicit setting/process would be better.