Add patch series for Marlin 2.1.2.1

[wireddown]

CR30-Users with Marlin 2.1.2.1

This PR takes the selections from #1 and applies them to Marlin 2.1.2.1, fixing two uncovered issues:

1. ✅ Scrambled bootscreen
   • A symbol changed names on 7 Feb 2021 (commit)
   • Fixed in patch 22
2. ✅ Power loss recovery fails
   • Does not home XY
   • Advances Z too far
   • Fixed in patch 23

Additional features enabled

• Hotend timeout
• Emergency parser
• Junction deviation
• S curve acceleration
• Input shaping for X and Y
• Sub-mm coordinates on the LCD screen
• (also several others)

Script

Add Powershell script get-and-patch-source.ps1 that fetches upstream Marlin firmware source and configuration and applies the patches in this PR. Checking new Marlin versions and branches is configurable from settings in the script.