delaytop: add delay max, timestamp and sorting for top latency analysis

From: Wang Yaxin <wang.yaxin@zte.com.cn>

Previously delaytop only showed average delays. This patch adds:

1. delay_max fields to track the maximum delay value for each delay type
   (cpu, blkio, irq, swapin, freepages, thrashing, compact, wpcopy)
   per task.

2. The -t/--type option displays only the specified delay type with avg/max
   values side by side, allowing focused analysis:
     delaytop -t cpu    # Show only CPU delay with avg/max
     delaytop -t wpcopy # Show Copy-on-Write delay with avg/max

3. Wall-clock timestamp when each maximum delay occurred, displayed in the
   MAX_TIMESTAMP column when using -t/--type option. This enables:
   - Identifying the time when a process experienced an abnormal delay max
   - Correlating delay max across multiple processes at the same timestamp
   - Cross-referencing with logs, traces, or other metrics at that time

4. When using -t/--type option, tasks are sorted by maximum delay value in
   descending order (largest delay first), enabling quick identification of
   top N processes with highest delay spikes.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>

Wang Yaxin (3):
  delaytop: add delay max for delaytop
  delaytop: add timestamp of delay max
  delaytop: sort by max delay to highlight top latency processes

 Documentation/accounting/delay-accounting.rst |  43 ++++
 tools/accounting/delaytop.c                   | 232 +++++++++++++++---
 2 files changed, 247 insertions(+), 28 deletions(-)

-- 
2.25.1