Optimize QQmlProfilerService

Having the profiler itself be as optimized as possible allows it to provide a more accurate representation of the performance of a QML app. The profiler has undergone a number of revisions since it was initially introduced, and probably has additional opportunities for optimization at this point. For example:

• The profiler never sends messages directly; they are always queued.
  • Can we delay more data conversions (QUrl->QString, char*->QString, etc) until sendMessages?
  • Can we remove the overhead of an extra function call to processMessage (e.g. can it be made inline)?
• With many of the RAII structures it seems we are checking enabled multiple times. For example in the constructor/destructor and also in startRange/endRange. Can some checks be removed, or can we effectively use Q_LIKELY/Q_UNLIKELY here?
• Can messages be compressed? For example, can range start and location be compressed into a single event in most cases (instead of needing both startRange and rangeLocation)? Are rangeLocation and rangeData ever redundant?