During `ReencodeDungeonCels`, extracts floor tile foliage into
a triangle with the floor frame and a separate 16-px tall `TransparentSquare`.
This means that the floor frames are now always triangles and
the foliage can be rendered directly without masking.
Dungeon graphics sizes:
Map | Frames | Foliage frames | Byte size | Before PR | After PR
-----|--------|---------------:|-----------:|----------:|----------:
Town | 3,803 | 41 | 2,317,832 | 2,242,056 | 2,242,190
L1 | 1,119 | 11 | 738,836 | 721,604 | 721,110
L4 | 1,091 | 6 | 603,140 | 584,500 | 584,242
RG99 binary size reduced by ~4 KiB: 2,426,380 bytes -> 2,421,388 bytes
Triangles in the dungeon CEL data have two redundant 0x00 pixels every other row.
Re-encodes the dungeon CEL data to remove these pixels in order to save RAM and simplify the rendering code.
Example RAM savings:
```
VERBOSE: Re-encoding dungeon CELs: 1,119 frames, 738,836 bytes
VERBOSE: Re-encoded dungeon CELs: 1,119 frames, 722,552 bytes
```
Performance remains the same. The rendering code is now a bit simpler.
Gleb Mazovetskiy