Add collar and preg prompt parts

Description and notes

Re-added CollarPromptPart to sdxl/pony prompt building that was removed without mention in !12208 (merged).

Also added PregPromptPart, if I broke something I'll try and fix it but it seems to work on my machine.

Merge Checklist

• I have read CONTRIBUTING.md
  • and
    • my code editor has
      • ESLint support enabled
      • TypeScript support enabled
      • some form of spell checker
        • We suggest using a spell checker compatible with cSpell if possible
    • my changes compile successfully and seem to work properly
    • I am using the simple compiler (simple-compiler.[bat or sh])
    • I am using the normal compiler (compile.[bat or sh])
    • this is my first merge request
    • the changes in this merge request comply with the coding style defined in CONTRIBUTING.md

Changes made

• Add collar and preg prompt parts