Implement supports for ObjectiveSense

[blegat]

Otherwise I get an error when changing the objective function as it think the issue is that ObjectiveSense is not supported, not that the model should be wiped out and copy_to should be called again

[klamike]

Isn't a corresponding setter required here for MOI to actually change the sense? Something like

function MOI.set(
    model::Optimizer,
    ::MOI.ObjectiveSense,
    sense::MOI.OptimizationSense,
)
    model.model.meta.minimize = isequal(sense, MOI.MIN_SENSE)
    return
end

[blegat]

Being supported means that it can either be set through MOI.copy_to (one-shot interface) or through MOI.set (incremental interface). Here, ExaModels only implements the one-shot so no need for MOI.set. Unless the solver supports efficient handling of resolve after problem modification, there is no need to implement it in the MOI interface. What will happen then is that the ExaModel model will be emptied and copy_to will be run again