Bigred Changes Part 2: Engineering And Reactor small touches (#4929)

# About the pull request

This PR does alot of floor detailing in the areas of engineering, filt
and their nightmare incerts

This PR also re-adds the reactor to the main file of bigred

# Explain why it's good for the game

Basically, every building in bigred uses the same floor tiles so I
wanted engineering and filt to have their own look

The reactor was removed from bigreds main file due to Xenos choosing to
nest in there causing the nested marines to die from radiation poisoning
that problem has since been removed and because the area that replaced
the reactor is a bland cave with no detailing whatever I believe that
readding and updating the reactor is the right choice to make
engineering a bit more visually interesting

this PR also removes the scattered engineering reactors from bigred
since they were added when the reactor was removed now all of bigreds
repairable engines are once again inside the reactor proper

# Testing Photographs and Procedure
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<summary>Screenshots & Videos</summary>

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screenshots and the `<details>` tags.

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# Changelog
:cl: SpartanBobby, GDS Pathe
maptweak: Updates bigred floortiles
maptweak: Re-adds reactor to bigred
/:cl: