Add per-process page fault counters to sysctl and procstat

[rkarahan80]

This commit introduces new sysctl OIDs and enhances procstat to display per-process minor and major page fault counts.

Kernel changes:

• Added new sysctl OIDs:
  • kern.proc.pid.<PID>.minflt (minor page faults)
  • kern.proc.pid.<PID>.majflt (major page faults)
• Implemented a sysctl handler in sys/kern/kern_proc.c that retrieves these values from the process's aggregated rusage statistics (p_ru.ru_minflt and p_ru.ru_majflt) after ensuring they are up-to-date by calling rufetchcalc().
• Defined KERN_PROC_PID_MINFLT (48) and KERN_PROC_PID_MAJFLT (49) in sys/sys/sysctl.h.

Userland changes (procstat):

• Added a new command-line option '-f' to procstat to display page fault counts.
• The previous '-f' option (for files) has been changed to '-F'.
• Created usr.bin/procstat/procstat_faults.c to implement the functionality for fetching and displaying these counts using the new sysctls.
• Updated usr.bin/procstat/Makefile to include the new source file.
• Updated the procstat.1 man page to document the new '-f' (faults) and revised '-F' (files) options.

This provides a convenient way for users and administrators to query the number of minor and major page faults a specific process has incurred, which can be useful for performance analysis and debugging.

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