Add Variable Views visible in FlatZinc

[Dekker1]

• Change modelling layer for directly using Views in Model
• Add detection for linear views in the FlatZinc
• Add bool2int support through integer view
• Add subject literal to Conflict type for non-root level conflicts
• Update Solver Debug implementation
• Update tracing for propagators

[codecov]

Codecov Report

Attention: Patch coverage is 50.72727% with 271 lines in your changes are missing coverage. Please review.

Project coverage is 54.87%. Comparing base (82f6e52) to head (2699dfc).

Files	Patch %	Lines
crates/huub/src/model/flatzinc.rs	0.00%	87 Missing ⚠️
crates/huub/src/model/int.rs	22.03%	46 Missing ⚠️
crates/huub/src/solver/view.rs	13.33%	39 Missing ⚠️
crates/huub/src/model/reformulate.rs	57.14%	21 Missing ⚠️
crates/huub/src/model/bool.rs	45.94%	20 Missing ⚠️
crates/fzn-huub/src/tracing.rs	0.00%	17 Missing ⚠️
crates/huub/src/helpers/linear_transform.rs	77.04%	14 Missing ⚠️
...ates/huub/src/solver/engine/propagation_context.rs	75.00%	13 Missing ⚠️
crates/huub/src/model/constraint.rs	44.44%	5 Missing ⚠️
crates/huub/src/solver/engine.rs	94.20%	4 Missing ⚠️
... and 3 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #29      +/-   ##
===========================================
+ Coverage    53.69%   54.87%   +1.17%     
===========================================
  Files           27       28       +1     
  Lines         2799     2954     +155     
===========================================
+ Hits          1503     1621     +118     
- Misses        1296     1333      +37     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.