Get rid of benchmark problem class constructors (facebook#2605)

Summary:
Pull Request resolved: facebook#2605

Context: Benchmark problems are sometimes created with class methods `SingleObjectiveBenchmarkProblem.from_botorch`, `SingleObjectiveBenchmarkProblem.from_botorch_synthetic`, and `MultiObjectiveBenchmarkProblem.from_botorch_multi_objective`, the former two now being identical. This creates the need for some tricky type annotations; to me, replacing these with functions is obviously cleaner. This will make it easier to consolidate classes in the future.

This PR:
* Replaces `SingleObjectiveBenchmarkProblem.from_botorch` and `SingleObjectiveBenchmarkProblem.from_botorch_synthetic` with `create_single_objective_problem_from_botorch`
* Replaces `MultiObjectiveBenchmarkProblem.from_botorch_multi_objective` with `create_multi_objective_problem_from_botorch`

Differential Revision: D60284484

Reviewed By: saitcakmak