Testing of plan execution, diff generation, and model reporting

[cereallarceny]

Description

We want to test three core pieces of functionality within our codebase after migrating to using PyTorch's iOS wrapper classes: plan execution, diff generation, and model reporting. We are not testing them at this time because the classes we've written for plans, tensors, and such are unmaintainable with the types of PySyft plans we'd like to be executing. In order to achieve such functionality, we'll be copying code from an unmerged PyTorch PR: pytorch/pytorch#25541. After that task is done, we'll want to test this functionality once and for all!

Type of Test

• Unit test (e.g. checking a loop, method, or function is working as intended)
• Integration test (e.g. checking if a certain group or set of functionality is working as intended)
• Regression test (e.g. checking if by adding or removing a module of code allows other systems to continue to function as intended)
• Stress test (e.g. checking to see how well a system performs under various situations, including heavy usage)
• Performance test (e.g. checking to see how efficient a system is as performing the intended task)
• Other...

Expected Behavior

We should have completely passing tests for plan execution, diff generation, and model reporting.

Additional Context

pytorch/pytorch#25541