Fix image processing on iOS

[ltatarev]

Following changes from #67, the iOS implementation had issues preventing grayscale and colorMatrix from working correctly:

• Processor Override: When both properties were set, each didSet independently overwrote lazyImageView.processors, so only the last-set property took effect.

• Cache Issues: All color matrices shared the same static identifier ("custom.colorMatrix"), causing incorrect cached images when different matrices were applied. Rendering same image with different filters in a list was impossible, since only the first colorMatrix would take affect and be applied to all other images.

Changes:

• Added updateProcessors() method that consolidates both processors into a single array, called by both didSet blocks. This allows both transformations to be applied.

• Skips the color matrix processor when an identity matrix is detected, avoiding unnecessary overhead.

• Replaced static identifier with hash-based generation (generateColorMatrixIdentifier()). Each unique matrix now gets a unique cache key, preventing collisions while allowing proper cache reuse for identical matrices.
  Format: "custom.colorMatrix.<16-char-hex-hash>"