class TestLimiter

There are a few tests in this suite which attempt to perform a _large_ number

of iterations of the test, typically looking for something like a race

condition regression. This can lead to problems in some worst case

scenarios. If the test is running in non KVM assisted emulation (as it would

on RISC-V, currently), and the test harness machine is very overloaded

(something which does happen, unfortunately), it is possible for a test to

not be able to perform its 1000 (for example) iterations before timing out,

even if everything is working correctly.

Since these tests tend to be looking for non-deterministic repros of races in

the case of regression, there really is no good number of iterations to pick

here. 1000 is a lot, but it does not mean that the test is guaranteed to

catch a regression (there is no number large enough to guarantee that). This

said, in worst case scenarios, the test can end up timing out and generating

flake.

So, add a small helper class in an attempt to balance these two issues. We'd

_like_ to run the test through X cycles, but if it is taking longer than Y

second to do so, we should probably simply print a warning call the test

done early. This way, we are still getting a lot of iterations in CI/CQ, but

hopefully not causing any false positive flake when things are not running

quickly in the test environment.