v0.8.0

HetaSimulator v0.8.0

Diff since v0.7.8

### Breaking changes
- OptimizationProblem interface added
- fit arguments changed, docs updated
- generate_optimization_problem func added to export
### Other changes
- heta-compiler v0.9.8
- Julia 1.9 removed from tests
- Fixed empty simulation results vector
- Solver choice docs updated

Merged pull requests:

• fix for empty vectors in simulations (#72) (@ivborissov)
• adds OptimizationProblem interface (#73) (@ivborissov)