Add ETW events that would measure application start up time.

This is a request from the runtime team, aligned with their Arm64 effort. Related to https://github.com/dotnet/runtime/issues/64993

As an example, here’s a pointer to how the perf lab does this. All of the start-up tests emit an event when they have completed start-up: [https://github.com/dotnet/performance/blob/23b05253055e3c5253bf4a1c8d4d767f33c2b77b/src/tools/ScenarioMeasurement/Startup/GenericStartupParser.cs#L8](https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fdotnet%2Fperformance%2Fblob%2F23b05253055e3c5253bf4a1c8d4d767f33c2b77b%2Fsrc%2Ftools%2FScenarioMeasurement%2FStartup%2FGenericStartupParser.cs%23L8&data=04%7C01%7CTatiana.Solyanik%40microsoft.com%7Cc3e0644499224ac8f73c08d9eb2a047e%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637799387966396924%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=pLz5axwT4EfpYxtAjsYiGIBarg43zoIXzRrvXOx3mdM%3D&reserved=0)