Re-factor SchedulingDecisions

[csegarragonz]

Move them from src/util/scheduling.cpp to src/batch-scheduler/SchedulingDecisions.cpp.

The diff is quite verbose because they are used around outside the batch-scheduler directory.
This should be reduced considerably when src/scheduler stops scheduling messages.

[codecov]

Codecov Report

Merging #342 (e22b97a) into main (07da690) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #342      +/-   ##
==========================================
- Coverage   82.37%   82.31%   -0.06%     
==========================================
  Files         101      102       +1     
  Lines        8143     8155      +12     
==========================================
+ Hits         6708     6713       +5     
- Misses       1435     1442       +7     

Files Changed	Coverage Δ
include/faabric/scheduler/Scheduler.h	42.85% <ø> (ø)
include/faabric/transport/PointToPointBroker.h	100.00% <ø> (ø)
src/batch-scheduler/BatchScheduler.cpp	100.00% <ø> (ø)
src/transport/PointToPointBroker.cpp	79.56% <ø> (ø)
include/faabric/batch-scheduler/BatchScheduler.h	78.57% <100.00%> (ø)
include/faabric/batch-scheduler/DecisionCache.h	100.00% <100.00%> (ø)
src/batch-scheduler/BinPackScheduler.cpp	97.12% <100.00%> (-0.09%)	⬇️
src/batch-scheduler/DecisionCache.cpp	86.84% <100.00%> (ø)
src/batch-scheduler/SchedulingDecision.cpp	100.00% <100.00%> (ø)
src/mpi/MpiWorld.cpp	77.63% <100.00%> (+0.02%)	⬆️
... and 3 more

... and 2 files with indirect coverage changes