New swamp clip

What's new:
===========
Yuzu found a new RTA method of indoors clipping into certain structures of collision tiles. This can be used in a lot of screens, but so far the only application for NMG was found by Kan, which is a clip that saves ~7s in Swamp in NMG.

(There is also a new clip in Ice, if you haven't seen it: https://pastebin.com/P1ipikM4)


How to do it:
=============
See https://media.discordapp.net/attachments/195826874847330304/676932407987011584/2020-02-11_18-26-01_Trim.mp4

1. Align with the south-most rails (Y=FB8)
2. Walk a bit left, and put down a Somaria around when Link is right below the stairs.
3. Walk into the corner between the left-side rails and the stairs (D60 FB0)
   You will push the Somaria block a little bit when doing this, which is part of the setup (pushes the block to where it needs to be).
4. From the corner (D60 FB0), move for 1f downwards (can menubuffer, swordbuffer, tap etc.)
5. Hold <^ (up-left) to go back into the corner. This should put you at D60 FAF.
6. Face left, slash and hold your sword.
7. Hold <^ (up-left) to clip. (Either start holding it during the slash, or start by pressing <, then go to <^)


NMG timing:
===========
Old route:
- Hookdash: 12'07
- Lonely Bari: 03'25
- Water lever room: 11'49
- C shaped room: 03'13
TOTAL: 30'34

New route:
- Hookdash: 5'50 (picks up arrows, but this can apparently be done 20-30f faster)
- Swamp clip: 12'30 (2 menues)
- C shaped room: 4'41
TOTAL: 23'01

Saving 7-8 seconds.


Technical info:
===============
This clip is like any old clip. The code for determining Link's movement in relation with collidable tiles is imperfect, and sometimes allows us to clip into things. This is similar to Kiki skip type clips (minus the teleport) in technical terms.

Note that just like with Ice Breaker, Somaria block is not strictly needed, it just makes it easier to perform RTA. Here's an example without the use of Somaria block: https://twitter.com/linus0505/status/1227247981713248258

Then there is the question of whether it's EG or not. In human terms, this screen looks like it has two layers (upper = brown floor; lower = green floor). However, those two layers are in technical terms the same layer.
Example: If it was possible to clip from the "lower" floor to the "upper" floor, you would not appear below the floor, like we generally do when we're talking about EG. This is because the game considers both of these as being on the same layer. It would be like clipping any old wall in a layer-less room (like Ice Breaker).

In technical terms, there _is_ one additional layer. It's just a square filled with water. This layer is present, and filled with water, even if you have pushed the water draining lever. So in a weird way, upper and lower floors are layer 0, and the water is layer 1. The water that you can see with your eyes, are purely graphical and have nothing to do with Link's interactions with those tiles (as is evident in this clip, since we appear to be on the lower floor, but on top of the water).

The reason you change from layer 0 to layer 1 and start swimming, if using the stairs like a normal person, is due to a group of tiles of "deep water" that is present right above the stairs: https://i.imgur.com/LiY5sx8.png (see the dark blue squares). Touching these will make Link jump into the water, and also changes the layer. By clipping past these "deep water" tiles and jumping to the lower floor, we don't touch them, and so we never start swimming nor change layers.

So it's not an "unintended layer change" (the layer does in fact never even change). It's more of a "skip touching the 'deep water' tiles" type of thing.