Add support for generalized samplers, OpenGL interop, etc.

This allows us to handle stuff like sampler2DRect or samplerExternalOES etc. transparently. As an aside, we also properly handle e.g. usampler2D (for UINT textures) as part of the same refactor.

Requires some more API breaks (especially with regards to the PL_SHADER_SIG_SAMPLER2D, but since these APIs are relatively new it shouldn't bite any users in practice. This should hopefully give us all the tools VLC needs.

changed milestone to %v2.66+

cc @alexandre-janniaux does this look good to you?

One notable omission is the inability to deal with rotated textures, which is a general pl_renderer limitation. I consider it out-of-scope for this release.

added 9 commits

• b3d516ae...09910b8c - 4 commits from branch master
• e15d4880 - gpu: add pl_tex_sampler_type to pl_tex objects
• 30bd2231 - dispatch: handle special sampler types
• e562b731 - shaders/sampling: handle PL_SAMPLER_RECT
• 663c8cb3 - opengl: add raw texture interop API
• bacc24a0 - shaders/sampling: generalize PL_SHADER_SIG_SAMPLER2D

Compare with previous version

Gonna merge this as-is since it's a relatively non-breaking change and it seems to line up well with the requirements I'm seeing. We can still make adjustments after the fact.

merged