Auto-bind filter shaders to the filter graphic

[davepagurek]

Resolves #6466
Resolves #6430
Resolves #2895

Changes:

• Automatically compiles shaders made via createFilterShader on the filter graphic context
  • This means you can start setting uniforms on them right away
• Removes copying when switching filter shaders
  • This is no longer necessary if you only use shaders made with createFilterShader
  • I kept some shader copying functionality in shader.copyToContext(someGraphic)
• Adds an error when you call shader() on a shader already compiled on a different context

Here's a version of the sketch from #6466 showing both shaders correctly receiving uniforms: https://editor.p5js.org/davepagurek/sketches/V-i6Chghn

PR Checklist

• npm run lint passes
• [Inline documentation] is included / updated
• [Unit tests] are included / updated

[aferriss]

This is amazing, three in one, thanks for pulling this together @davepagurek!