Allow any test field to be logged as well as allow tests to log arbitrary data

[vkarak]

This is a custom change introduced to @ZQyou's fork.

[vkarak]

Perhaps a more general solution to log any attribute of the RegressionTest would cover this and any future case.

[vkarak]

In addition to being able to log any attribute of a test, it would make sense to allow logging of arbitrary information per test basis. That could happen through another test field dedicated to this.