error msg more explicit wrt different interfaces

[lukasbiton]

Summary/Motivation:

As demonstrated in Issue 3130, the error message raised when a problem is unfeasible doesn't take into account the two different interfaces that can be used to create models: via contrib.appsi or via environ.SolverFactory.

Changes proposed in this PR:

For each of the appsi solvers, the error message raised now details the syntax more explicitly. The original issue was written using the HiGHS solver, but the following error message was added for Cbc, Cplex, Gurobi, Highs, Ipopt, and Wntr.

'A feasible solution was not found, so no solution can be loaded. '
'If using the appsi.solvers.Highs interface, you can '
'set opt.config.load_solution=False. If using the environ.SolverFactory '
'interface, you can set opt.solve(model, load_solutions = False). '
'Then you can check results.termination_condition and '
'results.best_feasible_objective before loading a solution.'

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[michaelbynum]

Thanks for this! Looks great!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (783872b) 88.33% compared to head (f7411c5) 88.33%.
Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
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- Coverage   88.33%   88.33%   -0.01%     
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  Files         833      833              
  Lines       92700    92700              
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- Hits        81889    81888       -1     
- Misses      10811    10812       +1     

Flag	Coverage Δ
linux	86.23% <ø> (ø)
osx	75.72% <ø> (ø)
other	86.43% <ø> (-0.01%)	⬇️
win	83.66% <ø> (-0.01%)	⬇️

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