Cleanup GPTL timers

This issue details some minor cleanups required for the GPTL timers in PIO1 and PIO2 to simplify timing outputs,

* Remove GTPL timers for internal functions, unless absolutely necessary. e.g. PIOc_createfile_int in PIO2
* All GPTL timers for internal functions should be prefixed as "PIO_:" (A suffix of underscore to indicate internal function timer)
* All GPTL timers for user API functions (e.g. PIOc_* in PIO2) should be prefixed as "PIO:".
* Add missing timers for user APIs . e.g. PIOc_create() in PIO2
* Add a separate timer to calculate the write I/O throughput (This timer will only include pio_put*, pio_write_darray, pio_sync and any logic in pio_closefile that flushes data to disk)