Expose P99 latency and support customizable IO testing with selective IO types and metrics

[derekbit]

• Customizable IO testing with selective IO types and metrics Users have the option to select specific IO types, including random read (randread), random write (randwrite), sequential read (seqread), and sequential write (seqwrite), as well as metrics like IOPS, bandwidth, and latency. There's no requirement to conduct all tests.

  =========================
  FIO Benchmark Summary
  For: test_device
  CPU Idleness Profiling: disabled
  Size: 100M
  Quick Mode: disabled
  =========================
  IOPS in ops (Read/Write)
                    Random:           15,013 / 8,874
                Sequential:          22,499 / 13,134
  
  Bandwidth in KiB/sec (Read/Write)
                    Random:        518,918 / 277,945
                Sequential:        652,231 / 305,601
  
  Latency in ns (Read/Write)
                    Random:        298,378 / 419,719
                Sequential:        295,757 / 414,594
  
  
  
  =========================
  FIO Benchmark Latency P99 Summary
  For: test_device
  CPU Idleness Profiling: disabled
  Size: 100M
  Quick Mode: disabled
  =========================
  Latency in ns (Read/Write)
                    Random:      667,648 / 1,028,096
                Sequential:      618,496 / 1,003,520
  

• Expose P99 latency Expose 99th percentile. It means that 99% of the requests should be faster than given latency.

Longhorn/longhorn#8254