Attempted fix on flaky counter tests

[JamesNK]

I noticed that #57259 is still flaky after the latest changes. 4 failures in the last 30 days.

For some reason I thought it would be a good idea to sum the results from the total request counter. This doesn't make any sense 🤷 Maybe I was thinking of RPS counter when I did it. Total request counter is pre-summed so change the test back to test the latest value.

I've also made a change to improve logging and debugging the counter methods.

[captainsafia]

LGTM overall!

Was the inaccurate totalRequestValues.WaitForSumValueAsync causing the flakiness or something else? I'd expect it to be a logical bug that would always cause the tests to fail instead of just being flaky.

[JamesNK]

Was the inaccurate totalRequestValues.WaitForSumValueAsync causing the flakiness or something else? I'd expect it to be a logical bug that would always cause the tests to fail instead of just being flaky.

Summing was always wrong for this value. But it is only a problem if it takes multiple seconds to get the right values. If the first set of values are correct then it doesn't have to sum and it passes.

I also much improved the logging for this test so if there are still problems then they should be more easier to observe.

[JamesNK]

/azp run

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