New deathmatch map: DM01 Entryway (#31533)

New deathmatch map: DM01 Entryway (#31533)

* added plastitanium walls and windows

* Added DM01 Entryway to pool of deathmatch arenas

* replaced non-occluding walls with occluding ones

* added more details and fluff to empty rooms and hallways; added floor drains around the map

* Fixed failing integration test

* fixed YML syntax error causing test failures. What kind of retard thought that using whitespace as structural syntax is a good idea?

* minor map changes

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Co-authored-by: Unisol <pavelyakushevich@gmail.com>