Fix bug in ETW trace code for AcquiredAppLock

[cgillum]

Problem Description

During an incident investigation, we saw the following error message logged by the ETW provider:

Event 300 was called with 2 argument(s), but it is defined with 4 parameter(s).

Impact

This error does not cause any exceptions. It just produces a logging error and prevents us from seeing any AcquiredAppLock events in App Service telemetry. The log should still get captured correctly in Application Insights, however, since that does not depend on the ETW provider.

Root Cause and Fix

Looking at the code, the problem seemed to be that we were passing a 2 to WriteEventCore when we needed to be passing a 4. Rather than fixing this directly, I decided we should just not use WriteEventCore (which is unsafe) and instead just use WriteEvent, which is safer and more consistent with our other logs.

As an aside WriteEventCore is useful as a performance optimization. However, this particular log event is written infrequently and therefore doesn't really benefit from a slightly more optimal code path.