This fixes the crash reported in
https://github.com/open-goal/jak-project/issues/2833
There was a memory bug here for a long time where our array of `VagCmd`
in `iso_queue.cpp` was too small. This caused GetVagCommand to return
bogus pointers, and sound code would write over other parts of memory.
Avoids blocking other IOP threads on IO.
Idk if it'll really help anything, but at least theoretically it might
stop some pathologically slow IO case from blocking the VAG buffer
switching.
Normally, when they allocate a VagCmd, they do a bunch of stuff to clear
all the status bits and reset things
in particular the InitVAGCmd function does a lot
but for the stereo command, they do a lot less:
Which means that the new_stereo_command can just have random status bits
left over from whatever the last user had.
we seem to end up in a state where byte21 is set, and this causes
everything else to be wrong and off-by-one dma transfer. My guess is
that the original game avoided this bug due to lucky timing that I don't
understand.
I think the fix of just clearing byte21 is ok because there's no way
that the old value of the byte is useful after the command is
repurposed.
Also fixed an original game bug in `loader.gc` on a method that's called
quite often, though I have no clue what erroneous behavior it could have
even caused.
Saves 16 bits and lets us align the `color_index` field properly.
This shouldn't improve or decrease performance by any noticeable amount
except maybe in really low end systems.
