'kitty' render style improvements

[AnonymouX47]

Continues #40

• Implements render method override for 'kitty' render style.
  • Adds method style arg to KittyImage.
  • Adds render method override field to 'kitty' style format spec.
• Implements ZLIB compression level control for 'kitty' render style.
  • Adds compress style arg to KittyImage.
  • Adds compression level field to 'kitty' style format spec.
  • Adds --kc/--kitty-compress style-specific CL option.
• Improves 'kitty' style render method selection for best drawing performance in different terminal emulators, in the CLI and TUI.