Support Features::MULTI_DRAW_INDIRECT on OpenGL

[Astralchroma]

Describe the solution you'd like
wgpu currently specifies that Features::MULTI_DRAW_INDIRECT is only supported on Vulkan, DirectX 12, and Metal, but not OpenGL despite the fact that from what I can tell, it is supported in OpenGL 4.3+ or if the extension ARB_multi_draw_indirect is available, ideally wgpu should support Features::MULTI_DRAW_INDIRECT on OpenGL on devices where it is available.

Describe alternatives you've considered

1. Not using OpenGL: On the low end, some people still have machines that are not capable of Vulkan, or do not support it very well.
2. Not requiring Features::MULTI_DRAW_INDIRECT: This means duplicating code to work with and without it.
3. Not using Features::MULTI_DRAW_INDIRECT: This means missing out on any potential improvements it brings.

Additional context
While I have yet to use Features::MULTI_DRAW_INDIRECT, I imagine I will end up wanting to use it at some point, and I imagine many others already do use it, or want to.