Review performance monitoring

[jeanbez]

Review performance monitoring systemwide with timing collection (function enter/exit).

Support for multiple levels of performance monitoring.

[TheAssembler1]

There are currently 3 macros used to capture different timing information in PDC:

1. PDC_TIMING: captures memory copy times, various I/O operation times, etc.
2. ENABLE_PROFILING: per function time, invocations, etc. Results printed to stdout.
3. ENABLE_TIMING: captures time of obtaining/releasing locks, region transfer times, and various rpc times, etc. Results saved in .csv.

The plan is to change PDC_TIMING so the output goes to stdout. Also I believe ENABLE_TIMING should be replaced with PDC_TIMING.

We should probably change the name of PDC_TIMING since the other configuration macros start with the prefix ENABLE_. However, the outdated timing code uses the macro ENABLE_TIMING. So I plan to replace the old timing code which uses ENABLE_TIMING with the new timing code which uses PDC_TIMING and then rename the macro PDC_TIMING->ENABLE_TIMING which is a bit confusing but I think this makes the most sense to stay consistent with the rest of the codebase.