Add a metric that would help us identify if a VM/Fuzzing process was coming under memory pressure.

[mgreisen]

Sometimes we've seen fuzzers get OOM's and we don't find out until later. Sometimes the virtual memory on a VM may not be enough.

It would be helpful to have a small set of perf counters that could tell us when there is memory pressure.

AB#162956

[tevoinea]

We should look into using the existing perf metrics provided by azure to get at available memory.