Fix snake_case filenames

Renamed a bunch of files, most of them one-off functions, to better fit
the general snake_case naming scheme. Also renamed some awfully long filenames.

engine/gfx/load_push_oam.asm

@@ -0,0 +1,21 @@
+WriteOAMDMACodeToHRAM:: ; 4031
+	ld c, hTransferVirtualOAM - $ff00
+	ld b, .PushOAMEnd - .PushOAM
+	ld hl, .PushOAM
+.loop
+	ld a, [hli]
+	ld [$ff00+c], a
+	inc c
+	dec b
+	jr nz, .loop
+	ret
+
+.PushOAM: ; 403f
+	ld a, HIGH(wVirtualOAM)
+	ld [rDMA], a
+	ld a, NUM_SPRITE_OAM_STRUCTS
+.pushoam_loop
+	dec a
+	jr nz, .pushoam_loop
+	ret
+.PushOAMEnd