vkd3d-shader/ir: Properly support texldb and texldp.
We are currently misscompiling .SampleBias() and tex2Dbias() for SM1 because we are failing to lower sample bias so that the bias ends up in the .w component which is required for the texldb instruction (patch 1/4).
In addition to that, we are not properly lowering texldb in ir.c, we only lower plain VKD3DSIH_TEX into VKD3DSIH_SAMPLE disregarding the flags, that is fixed for texldb in patch 2/4.
While we properly emit texldp for tex2Dproj() we are not testing it so patch 3/4 is introduced. We are not lowering this texldp in ir.c, so patch 4/4 takes care of that.