Miscellaneous updates and updates to documents

[jimmyjon711]

Major Changes in this PR

• AFC-28 Added ability to change stepper current when printing
• AFC-25 Added a boolean flag to PREP so that TCMD assignment does not happens twice in a single restart
• AFC-29 Added a check during prep load to make sure print is not printing,homing or moving as this would normally crash klipper
• Added comments to configuration variables to help aid in auto documentation of config variables
• Added features document to put features of AFC. Added bypass, print current and ram sensor to this document.

Notes to Code Reviewers

How the changes in this PR are tested

Testing results from trying to load printer when homing/moving

Testing for setting different current

Tool load:
    // Tool Change - None -> leg1
    // Loading leg1
    // Run Current: 0.61A Hold Current: 0.61A Home Current: 0.80A          # First sync to extruder for people using a toolhead sensor
    // Run Current: 0.80A Hold Current: 0.80A Home Current: 0.80A          # Unsync to extruder for ramming
    // Run Current: 0.61A Hold Current: 0.61A Home Current: 0.80A          # Sync back to extruder once ramming is done
    // New rotation distance after applying factor: 5.222222222222222
    // TURTLENECK buffer enabled
    // leg1 is now loaded in toolhead

PREP - Current is set to print current to lane that is loaded into toolhead
    // Run Current: 0.61A Hold Current: 0.61A Home Current: 0.80A
    // LEG1 tool cmd: T0  LOCKED AND LOADED in ToolHead

Tool unload
    // Unloading leg1
    // AFC_Cut: Cut Filament
    // AFC_Park: Park Toolhead z_safe: 14.0
    // Run Current: 0.80A Hold Current: 0.80A Home Current: 0.80A       # Unsyncing from extruder for buffer retract
    // Run Current: 0.80A Hold Current: 0.80A Home Current: 0.80A       # Unsyncing from extruder for long retract

Prep being called again after prep being automatically ran does not output error

PR Checklist: (Checked-off items are either done or do not apply to this PR)

• I have performed a self-review of my code
• CHANGELOG.md is updated (if end-user facing)
• Sent notification to software-design channel requesting review