[Bridges] fix bridges before final_touch and after bound changes

[chriscoey]

Before final_touch runs, SOS1ToMILPBridge, SOS2ToMILPBridge and IntegerToZeroOneBridge each report a ScalarAffineFunction-in-EqualTo constraint that they have not created yet. The bridged model then under-counts its equality constraints, and since ListOfConstraintTypesPresent skips any type whose count is 0, copy_to can silently drop a user's equality:

import MathOptInterface as MOI
model = MOI.Bridges.Constraint.SOS1ToMILP{Float64}(MOI.Utilities.Model{Float64}())
x = MOI.add_variables(model, 3)
MOI.add_constraint.(model, x, MOI.Interval(0.0, 2.0))
MOI.add_constraint(model, 1.0 * x[1] + 1.0 * x[2], MOI.EqualTo(1.0))
MOI.add_constraint(model, MOI.VectorOfVariables(x), MOI.SOS1([1.0, 2.0, 3.0]))
F, S = MOI.ScalarAffineFunction{Float64}, MOI.EqualTo{Float64}
MOI.get(model, MOI.NumberOfConstraints{F,S}())  # 0
dest = MOI.Utilities.Model{Float64}()
MOI.copy_to(dest, model)
MOI.get(dest, MOI.NumberOfConstraints{F,S}())   # 0

IndicatorToMILPBridge has a similar problem, and its ListOfVariableIndices also throws TypeError: in typeassert, expected MathOptInterface.VariableIndex, got a value of type Nothing, so copy_to fails. With MOI.instantiate(HiGHS.Optimizer; with_cache_type = Float64, with_bridge_type = Float64), writing the model to an LP file before optimize! drops the equality in the SOS case and throws in the indicator case.

These bridges now report no variables or constraints until final_touch has created them.

While here, I fixed the ZeroOne count of ReifiedCountDistinctToMILPBridge, which was -2 before final_touch, and IndicatorToMILPBridge keeping a deleted constraint index after a bound change (empty instead of empty!). IntegerToZeroOneBridge also kept its old expansion after a bound change between final_touch calls: widening an integer x from [0, 3] to [0, 7] left x - y1 - 2 y2 == 0 in the model, so x still could not exceed 3.