Add support for IA palettes

[Dragorn421]

Currently ci images are hardcoded in build_from_png as using rgba16 palettes. This adds support for choosing between a rgba16/ia16 palette by using a ci[48]_{rgba16,ia16} suffix. The simple ci[48] suffix remains used for extraction and is synonym to ci[48]_rgba16.

Inspired by fast64 PR Fast-64/fast64#719

---

Testing this feature was done thus:

Details

diff --git a/assets/objects/object_link_child/object_link_child.c b/assets/objects/object_link_child/object_link_child.c
index a7062de65..2dc1d6006 100644
--- a/assets/objects/object_link_child/object_link_child.c
+++ b/assets/objects/object_link_child/object_link_child.c
@@ -197,7 +197,7 @@ u64 gLinkChildSlingshotSeedTex[TEX_LEN(u64, gLinkChildSlingshotSeedTex_WIDTH, gL
 };
 
 u64 gLinkChildHandTLUT[] = {
-#include "assets/objects/object_link_child/gLinkChildHandTex.tlut.rgba16.inc.c"
+#include "assets/objects/object_link_child/gMyTestTLUT.tlut.ia16.inc.c"
 };
 
 u64 gLinkChildSwordsTLUT[] = {
@@ -215,7 +215,7 @@ u64 gLinkChildSwordTLUT[] = {
 #define gLinkChildHandTex_WIDTH 16
 #define gLinkChildHandTex_HEIGHT 16
 u64 gLinkChildHandTex[TEX_LEN(u64, gLinkChildHandTex_WIDTH, gLinkChildHandTex_HEIGHT, 8)] = {
-#include "assets/objects/object_link_child/gLinkChildHandTex.ci8.inc.c"
+#include "assets/objects/object_link_child/gLinkChildHandTex.ci8_ia16.tlut_gMyTestTLUT.inc.c"
 };
 
 #define gLinkChildKokiriSwordSheathTex_WIDTH 16

+ cp extracted/VERSION/assets/objects/object_link_child/gLinkChildHandTex.ci8.png assets/objects/object_link_child/gLinkChildHandTex.ci8_ia16.tlut_gMyTestTLUT.png

+ changing gsDPSetTextureLUT(G_TT_RGBA16) to gsDPSetTextureLUT(G_TT_IA16) in extracted/VERSION/assets/objects/object_link_child/gLinkChildLeftFistAndBoomerangNearDL.inc.c (bad; don't modify extracted!)

then building and in-game hold the boomerang to see link's gray hand up close

This tests the "shared tlut" path in build_from_png. very similarly the single tlut user path can be tested (and it works too!)