broadcom/compiler: prefer reconstruction over TMU spills when possible

We have been reconstructing uniforms for a while, but we can do this in more scenarios, namely instructions which result is immutable along the execution of a shader across all channels.

By doing this we gain the capacity to eliminate TMU spills which not only are slower, but can also make us drop to a fallback compilation strategy.

Shader-db results show a small increase in instruction counts caused by us now being able to choose preferential compiler strategies that are intended to reduce TMU latency. In some cases, we are now also able to avoid dropping thread counts:

total instructions in shared programs: 12658092 -> 12659245 (<.01%)
instructions in affected programs: 75812 -> 76965 (1.52%)
helped: 55
HURT: 107

total threads in shared programs: 416286 -> 416412 (0.03%)
threads in affected programs: 126 -> 252 (100.00%)
helped: 63
HURT: 0

total uniforms in shared programs: 3716916 -> 3716396 (-0.01%)
uniforms in affected programs: 19327 -> 18807 (-2.69%)
helped: 94
HURT: 50

total max-temps in shared programs: 2161796 -> 2161578 (-0.01%)
max-temps in affected programs: 3961 -> 3743 (-5.50%)
helped: 80
HURT: 24

total spills in shared programs: 3274 -> 3266 (-0.24%)
spills in affected programs: 98 -> 90 (-8.16%)
helped: 6
HURT: 0

total fills in shared programs: 4657 -> 4642 (-0.32%)
fills in affected programs: 130 -> 115 (-11.54%)
helped: 6
HURT: 0