Cache reflection lookup for TransactionID in Net Core logs

[snakefoot]

No need to perform the reflection-dance for every LogEvent (Introduced with #94):

stackify-api-dotnet/Src/StackifyLib/Internal/Logs/LogQueue.cs

Lines 201 to 204 in ac13f57

	var traceContextProp = callContextType.GetProperty("TraceContext")?.GetValue(null);
	if (traceContextProp != null)
	{
	var reqIdProp = traceCtxType.GetProperty("RequestId")?.GetValue(traceContextProp)?.ToString();

Should cache the lookup of callContextType.GetProperty("TraceContext") and traceCtxType.GetProperty("RequestId").

var traceContextProp = _callCtxTraceContextPropInfo.GetValue(null);
if (traceContextProp != null)
{
       var reqIdProp = _traceCtxRequestIdPropInfo.GetValue(traceContextProp)?.ToString();
}