BenchmarkTools dependency

[schillic]

The BenchmarkTools dependency seems not really necessary as it is only used in the Benchmarks folder. Could it be removed?

[odow]

This would be a breaking change, but it's a pretty minor one, and the MOI.Benchmarks submodule is not widely used. We could consider moving it to a package extension that requires the user to write using BenchmarkTools, which seems like a reasonable compromise. However, I'd prefer not to make a breaking change.

What is the motivation? Is BenchmarkTools a problem for loading times?

[schillic]

I was just surprised to see that package in the precompilation and thought this was an oversight. If there is a reason to have this part of the sources, then of course it should stay 👍

[odow]

If Julia had support package extensions when we first released MOI, it probably wouldn't have been a submodule. But it is what it is now. At one point we decided to go the monorepo route. It has upsides and downsides.