Add config file support for constants and test control (#4337)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4337

Now that the tool is getting larger, a configuration file for defining which tests to run and which to skip, as well as specifying some values like thresholds and ranges, comes in handy. This diff adds support for a JSON config file with specifications for each test.

Reviewed By: jorgep31415

Differential Revision: D60060188

fbshipit-source-id: d6ee9cbff52b3ab13e9a06a42dd54aec002fae11