Add additional WebGL filter stress scenarios to visual regression suite

[aashu2006]

Increasing access

Adds more WebGL filter scenarios to the visual regression suite so rendering issues can be caught earlier. This makes it easier to verify changes and reduces the chance of unnoticed breakage across releases.

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build process
• Unit testing
• Internationalization
• Friendly errors
• Other (specify if possible)

Feature enhancement details

While working on #8549 , I manually tested a few additional WebGL filter interaction scenarios that are not currently covered by the visual regression suite.

The current suite covers individual filters and some chained combinations, but does not cover:

• Filters applied after texture() on WebGL geometry
• Filters on createGraphics(WEBGL) buffers
• Filters after resizeCanvas()
• Filters with pixelDensity(2)
• Additional chained combinations beyond existing coverage

These scenarios behaved consistently across versions during manual testing. It may be useful to formalize them into automated visual tests to improve regression detection in future releases.

[aashu2006]

This issue is for visibility of stress scenarios discovered while working on #8549 .