🏴‍☠️ Remove type piracy 🏴‍☠️

[odow]

Please don't do this:

OSQP.jl/test/MOI_wrapper.jl

Lines 56 to 61 in 763ad7f

	# FIXME: type piracy. Needs https://github.com/jump-dev/MathOptInterface.jl/issues/1310
	function MOI.get(optimizer::MOIU.CachingOptimizer, attr::MOI.ConstraintPrimal, ci::MOI.ConstraintIndex)
	# FIXME `get_fallback` should do this first line
	MOI.check_result_index_bounds(optimizer, attr)
	return MOI.Utilities.get_fallback(optimizer, attr, ci)
	end

Not sure why it's implemented, but we're considering something similar: jump-dev/MathOptInterface.jl#1310

[blegat]

This is the reason, note that the same issue is mentioned in the comment line 56.