This should fix the janky falling off steep slopes and let you cling to them.
Because when falling off a sector the edge of the player must not intersect
the edge of the higher sector, it is trickier than step up. The height
difference at the line must be stored to be useful.

This is for slopes. When moving across a slope the height changes. Therefore
compare the height at the edge where slopes meet so only a wall will block the
player, and not a very steep slope.

Changes:
- "waypoint ID" is now tag (previously angle)
- "next waypoint ID" is now angle (previously Z height)
- Z height is Z height
- Radius is controlled by args[0]
- "is finish line" is controlled by args[1]
- Waypoint parameters linedef, riser things, and anchor things will not do anything in UDMF mode
- Non-UDMF maps are unaffected

(I did the same change for UDMF too but it may be wrong; I don't have a test map for it though so I guess we'll see later)

Yes I know it's pointless, but still...

I started this in another commit and forgot to fully finish it. Also allows attacking bot-controlled players who won

Move P_SpawnMapThings before P_SpawnSpecialsThatRequireObjects.

Do not remove special from lines with ML_NETONLY or ML_NONET until after
slopes are spawned.

- Fixed last place elimination not working (again)
- Replaces squishing from level geometry with good old fashioned crush death

Slopes in a few maps are really broken ... think it's anchors, I'm gonna leave that to jart :V

Revert a bruh moment from 2.2's development where, in order to fix statues and spikes from being visible on the death pit in CEZ, I made any object that comes into contact with a death pit and isn't on a whitelist delete itself.

(Now the Chao at the start of Sonic Speedway don't die immediately.)

Kart's manual player friction adjustments were being called after movefactor was reset, meaning friction changed but movefactor was default, essentially creating old 2.1 friction again

(Also removed a bunch of instances of PF_SPINNING since we haven't used it)

Vertex snapping 'slope anchors'

See merge request KartKrew/Kart!317