[breaking] remove automatic_copy_to

[odow]

Closes #1503

[joaquimg]

docs could be a bit more direct:

... The function
[`MathOptInterface.supports_incremental_interface`](@ref) can be used to check
whether `dest` supports the copying a model incrementally.

... The function
[`MathOptInterface.supports_incremental_interface`](@ref) can be used to check
whether this function will work since it will check wether `dest` supports the copying of a model incrementally.

[odow]

It seems crazy, but this has been sitting here since MOI 0.2.0! 1ae8661

[blegat]

I'm wondering whether it makes sense to remove this error.
MOI.supports_incremental_interface is what is used by instantiate.
Would there be a case where you want instantiate to add a cache but you would still like to be able to call default_copy_to?
Removing the error is nonbreaking so it might be fine for now

[odow]

This check is trivial and will be in-lined. It also prevents a later error like "add variable not allowed" in some cases. I'd suggest we leave it in, at least until all the solvers are updated. We could remove it for 1.0 if it's not needed.

[blegat]

This check is trivial and will be in-lined

Yes, I was not worried about peformance

I'd suggest we leave it in, at least until all the solvers are updated. We could remove it for 1.0 if it's not needed.

Sounds good