Create integration test for renaming Windows system metric

[SaxyPandaBear]

The logic for deriving the default name for Windows metrics differs from Unix. Rather than using a _ to separate, on Windows, the agent uses to separate. For example, instead of cpu_time_active, for the CPU plugin, the agent would hypothetically decorate the metric as cpu time_active. A bug was identified where we weren't properly renaming the metric when the prefix is omitted in the rename configuration, e.g.: "rename": "time_active" on Linux. The integration test that checks this on Linux is failing in our staging repo. There is nothing that would have caught this for Windows, as of right now. We need to add an integration test for that edge case.