Revert "The Resprite: Diagonal Reinforced Wall, Greyscale Decal Cleanup, Secret Doors"

[MilonPL]

About the PR

Reverts #1842

Why / Balance

Looks like it was merged without approval from velcro or anyone going over the yaml
Maintaining this is hellish (because frontier code) and I kinda gave up on fixing all of the issues + the sprites collide with ours anyways. The secrets door are buggy when being opened, and you can spot them because of the sprite anyways. That PR probably should've been split instead of cherry picking and fixing things at once.
If someone wants to pick the latest changes from frontier and resprite the diagonal walls, this could be brought back.

[github-actions]

RSI Diff Bot; head commit 91a8438 merging into 6a80988
This PR makes changes to 1 or more RSIs. Here is a summary of all changes:

Resources/Textures/DeltaV/Decals/Overlays/greyscale.rsi

State	Old	New	Status
checkerNESW			Removed
checkerNWSE			Removed
diagonal			Removed
diagonal_checker_a			Removed
diagonal_checker_b			Removed
fulltile_overlay			Removed
halftile_overlay			Removed
halftile_overlay_180			Removed
halftile_overlay_270			Removed
halftile_overlay_90			Removed
quartertile_overlay			Removed
quartertile_overlay_180			Removed
quartertile_overlay_270			Removed
quartertile_overlay_90			Removed
threequartertile_overlay			Removed
threequartertile_overlay_180			Removed
threequartertile_overlay_270			Removed
threequartertile_overlay_90			Removed

Resources/Textures/_NF/Structures/Doors/secret_door_reinforced.rsi

State	Old	New	Status
assembly			Removed
closed			Removed
closing			Removed
open			Removed
opening			Removed

Resources/Textures/_NF/Structures/Doors/secret_door_shuttle.rsi

State	Old	New	Status
assembly			Removed
closed			Removed
closing			Removed
open			Removed
opening			Removed

Resources/Textures/_NF/Structures/Doors/secret_door_uranium.rsi

State	Old	New	Status
assembly			Removed
closed			Removed
closing			Removed
open			Removed
opening			Removed

Resources/Textures/_NF/Structures/Doors/secret_door_wood.rsi

State	Old	New	Status
assembly			Removed
closed			Removed
closing			Removed
open			Removed
opening			Removed

Resources/Textures/_NF/Structures/Walls/solid_reinforced_diagonal.rsi

State	Old	New	Status
state0			Removed
state1			Removed

Resources/Textures/_NF/Structures/Walls/uranium_diagonal.rsi

State	Old	New	Status
state0			Removed
state1			Removed

Resources/Textures/_NF/Structures/Walls/wood_diagonal.rsi

State	Old	New	Status
state0			Removed
state1			Removed