Vents, scrubbers, freezers, more - OCD

This is kind of a big one..
* Removes edited values for vents, scrubbers which were the same as the default values (or almost the same, such as a target pressure of 100, 101, etc.).
* Ensures that custom vents have proper \*_default settings.

These two changes greatly reduces the number of vent/scrubber variants.

* Ensures that vents display the appropriate icon in the editor.

* Ensures freezers display the appropriate icon in the editor and cleans up default vars.

This reduces the number of freezer variants.

* Replaces a couple of airless turfs in medical with proper gas filled variants.

Also includes #5729.