Allocation-free access to evaluator

[blegat]

I did this some months ago in an attempt to see if we could get allocation-free iterations after jump-dev/MathOptInterface.jl#2740.
Before this PR, it relies on calling MOI.eval_objective(model, x) which access model.nlp_data.evaluator which is type-unstable since the type of evaluator is not concrete:
https://github.com/jump-dev/MathOptInterface.jl/blob/034a5272dad29a233783cc49ed7e15195450dd96/src/nlp.jl#L176
So the fix in this PR is to give to Ipopt closures that capture the evaluator, not the model.
Now even after this, we're not allocation-free yet because there is the type-instability in accessing

Ipopt.jl/src/C_wrapper.jl

Lines 18 to 21 in 077843b

	eval_f::Function
	eval_g::Function
	eval_grad_f::Function
	eval_jac_g::Function

We can add the type of these functions as parameters to IpoptProblem but then we need to modify this type-assert:

Ipopt.jl/src/C_wrapper.jl

Line 35 in 077843b

prob = unsafe_pointer_to_objref(user_data)::IpoptProblem

and I'm not sure how to make it work with @ccallable

Ipopt.jl/src/C_wrapper.jl

Lines 190 to 191 in 077843b

	eval_f_cb = @cfunction(
	_Eval_F_CB,

As discussed during the JuMP-dev hackathon, maybe #514 could help.