Fixed Rep having the same int name

[steam-test1]

Currently it names them i0 even if there's multiple loops

[AndresTraks]

Currently the idea is that the loop variable name is incremented for each rep/loop instruction and decremented for each endrep/endloop, so you get i0 in outer loops , i1 in inner loops and so on. If there are multiple loops on the same level, then the name i0 should be fine, because each loop variable is in the scope of its own loop.

I didn't realize that in previous versions of HLSL, the loop variable was contained in the scope outside of the loop, which would cause a problem. https://devblogs.microsoft.com/directx/hlsl-2021-migration-guide/ Visual Studio still gives a warning if i0 is used twice, but FXC will compile it.

This change doesn't seem consistent either, because the variable name is still decremented at endrep/endloop, so the name could still end up being reused. Also, the same logic isn't applied to the loop instruction as for rep. I'll think about it. We should also check that a loop variable isn't named the same as some user-defined global variable, but that'll take a while to implement.