[Prepare for next release] Reimplement windows

[darkevilmac]

Windows get their own ticket separate from shapes, there's some overlap here but the placement logic and sheer quantity of variations makes this a bit more tricky.

• Implement placement logic.
• Implement custom model resolution strategy for the variations.
• Determine the most performant method for calculating bounds.
• Implement "smart" version of windows that behaves more like vanilla.
• Investigate potential for "offset" windows being placed at the front or back of a block instead of just the middle.

Please note that all release preparation tickets are locked to contributors, these aren't for feature suggestions they are simply for tracking progress