Re-land fixes the crash when drawing with no bound Program executable.

Currently we track feedback loops by counting the times a Texture is
bound as a sampler or image in a particular context. This is a bit
tricky because Texture bindings change frequently. Relative to the
number of times we need to check for a feedback loop this causes excess
overhead.

Usually Framebuffers have a low number of Textures bound (in many cases
just 1). And Textures aren't usually bound to many different FBOs. So
instead of counting the number of times a Texture is bound as a sampler
or image we will track the Framebuffers that the Texture is bound to.

This CL adds a small vector class to gl::Texture which tracks all the
Framebufer Serials of its bound Framebuffers. We can use this set to
quickly check if there's any potential feedback loop between the a FBO
and this Texture.

We also update the feedback loop check to use this new method. We will
be able to remove the old counting method when we switch the Vulkan
feedback loop handling to use the new tracking in this CL.

Bug: angleproject:4500
Bug: angleproject:4959
Change-Id: If2bd25b08298a99f5e64b4055137f9154b0f0860
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2365595Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>