Improvements to blood and gibs

[CheffieGithub]

About the PR

blood.dmi has have been moved to obj/decals/blood/ along with martian and flock blood in their own files.
gibs have been moved out of blood.dmi into obj/decals/gibs/ along with martian, robot and flock gibs in their own files.

All of the blood in blood.dmi has been made greyscale and the unused icons have been removed. This means that coloured blood will correctly show on these icons.

Updated luminol overlay application.

Added a new atom forensics varible forensics_blood_color, solely for applying colour to the human blood overlays at the minute.

Improved /mob/living/carbon/human/EnteredFluid by allowing tracking and blood application for hemolymph and changeling blood.

Reduced proc calls when splashing blood onto humans, these procs will only update the specific clothing covered instead of all.

Improvements and fixes to /atom/proc/add_blood.

Replace varedited mystery meat with a randomised grody subtype with similar icons and names due to needing to change the icon anyway.

I looked for all the references for applying blood and icons but its possible I may have missed something so im adding a disclaimer to the changelog.

fixes #7207
fixes #6347

Known issue is with muantraces with offsets for things, as an optimisation I directly called update_X() proc when adding blood but these need to handle not having offsets handed in or have the blood parts taken out into their proc.

Why's this needed?

Pali wanted the icons to be made white, other changes were to let the colours work properly and for my sanity while working with blood code. Should be better to find blood and gibs related DMIs in future.

Changelog

(u)Cheffie
(*)Hemochromia, Colorful Reagent and some Mutantraces now correctly change the colour of created blood decals and overlays when bleeding. paint the halls! reagent pools of blood are uneffected.
(+)Internal changes to icons may possibly lead to some missing or white gib / blood icons, report these if you see them!

[pali6]

!merge_upstream

[github-actions]

Merging upstream failed:
https://github.com/goonstation/goonstation/actions/runs/5941559753

[Nebulacrity]

Holy shit, nice! Been waiting for this for quite some time.