freedreno: Fix hangs trying to push too many constants

Fix for #3049 (closed): Fix the a6xx per-shader limit on constbuf, respect it in UBO analysis (even in the presence of large ubo 0) and immediates-to-consts conversion.

Note that we still won't get the perf we might hope, because if you have an indirect load you can't upload due to max consts, we'll end up uploading the contents in both the const file (filling it up) and as a LDC UBO, then use LDC. It should be pretty easily fixable, but I would like vulkan CI in place since it will affect vulkan more than the rest of this series (it'll touch push constant offsetting).