Do not reset scissorTest in WEBGLRenderPass

[Pessimistress]

This is causing a regression in deck.gl's picking and collision filter. Calling device.beginRenderPass() or renderPass.setParameters() will always set scissorTest to false.

It could be argued that beginRenderPass is expected to reset the state (questionable because it doesn't do this to any other parameter), however setParameters() as a public method should never affect a value not present in the argument.

Alternatively we can allow scissorRect to accept null on which we disable scissor test.

Change List

• Only sets scissorTest if scissorRect is present

[ibgreen]

Yes I think it makes sense. We want to emulate WebGPU parameter semantics in WebGL but WebGPU doesn't support inheriting a dirty context so WebGL module has some freedom to define how this works.

Some comments may be appropriate and maybe even a short section in the parameters page or separate about attaching to existing WebGL contexts