Replace go with gridops

[keremakdemir]

Overview

This PR replaces the go package with gridops, a ground-up refactor of the production cost model focused on solver performance, warm-start support, and a cleaner API. The package is renamed from go to gridops.

Core Architecture Change: AbstractModel → ConcreteModel

• go used Pyomo's AbstractModel, requiring a preprocessor step to generate a large .dat file from multiple CSV/NPY files before each simulation.
• gridops uses Pyomo's ConcreteModel, built directly from Python data structures. All CSV/NPY files are loaded once into a dictionary. The model is constructed once and reused across all 365 horizons — only mutable parameters (demand, renewables, fuel prices, outages, etc.) are updated between solves.

Performance Improvements

• Variable bounds replace explicit constraint rows — Flow, SoC, Charge, and Discharge variables now carry their bounds directly instead of through separate constraint rows, reducing LP size.
• Pre-computed sparse lookup dicts (_gens_at_bus, _lines_at_bus, _storage_at_bus, etc.) eliminate Cartesian product iteration in constraint and objective construction.
• Default solver parameters for HiGHS and Gurobi — automatically set when warmstart=False for both HiGHS and Gurobi interfaces to speed up the convergence.
• Named constants replace static numbers (SLACK_PENALTY, RENEWABLE_GEN_COST, PU_BASE_MVA, etc.).

New: Warm-Start Support

• New warmstart parameter on Model (default False), overridable per run() call.
• _resolve_warmstart() enforces solver-specific policies:
  • appsi_highs: warm-start uses simplex with crossover off (persistent basis reuse); cold-start defaults to IPM + crossover.
  • appsi_gurobi: warm-start sets LPWarmStart=1; cold-start sets LPWarmStart=0 + PreDual=1.
  • gurobi: warm-start auto-switches to appsi_gurobi with a warning.
• Cold-start horizons call clearSolver() on the APPSI persistent interface to force fresh presolve.

API Changes

• complexity parameter removed — was always "multi", no longer needed.
• CPLEX removed, appsi_gurobi added as a supported solver interface.
• highspy>=1.10.0 added as a required dependency.
• numpy upper bound (<2) removed.

Retry Logic

• Retry configuration centralized in a module-level HIGHS_RETRY_DEFAULTS dict, overridable via retry_options parameter on run() (replaces long positional argument lists).
• Gurobi retry now sweeps random seeds only (with a separate MAX_RANDOM_SEED_GUROBI cap).
• New fresh_start and clear_restart parameters for restart file lifecycle management.

Build System & Tests

• setup.py + requirements.txt → single pyproject.toml (Hatchling backend).
• New tests: test_configuration.py, test_solvers.py, test_west_integration.py (ConcreteModel construction validation). Expanded test_utilities.py coverage (restart file versioning, backoff, cleanup).