IpcClient suggestions

- This regex pattern is never used: https://github.com/dotnet/diagnostics/blob/master/src/Microsoft.Diagnostics.Tools.RuntimeClient/DiagnosticsIpc/IpcClient.cs#L20
- Instead of listing all files and allocating a new regex for each (the temp folder can be big) it's possible to pre-filter the listing https://github.com/dotnet/diagnostics/blob/master/src/Microsoft.Diagnostics.Tools.RuntimeClient/DiagnosticsIpc/IpcClient.cs#L45 with `Directory.GetFiles(IpcRootPath, $"dotnet-diagnostic-{processId}-*")`
- The expected file is created with a delay after the app is starting. On my machine adding a delay of 100ms solved the issue. My scenario is that I am starting an app with `Process.Start` then calling into `EventPipeClient.CollectTracing()`. It would fail with the `PlatformNotSupportedException` thrown because the file would not be found.