mesa/st: glsl_to_tgsi: tie in new temporary register merge approach

mesa/st: glsl_to_tgsi: tie in new temporary register merge approach

This patch replaces the old register lifetime estiamtion and
rename mapping evaluation with the new one.

Performance to compare between the current and the new implementation
were measured by running the shader-db in one thread.

-----------------------------------------------------------
                    old          new(std::sort)

---------------- time ./run -j1 shaders --------------------

  real              5.80s          5.75s
  user              5.75s          5.70s
  sys               0.05s          0.05s

---- valgrind --tool=callgrind --dump-instr=yes------------

 merge               0.08%         0.18%
 estimate lifetime   0.02%         0.11%
 evaluate mapping  (incl=0.3%)     0.04%
 apply mapping       0.03%         0.02%

---   perf (approximate because of statistic sampling) ----

merge (total)        0.09%         0.16%
estimate lifetime    0.03%         0.10%
evaluate mapping  (incl=0.02%)     0.04%
apply mapping        0.04%         0.04%

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>