This patch add new -T option to show timestamp for each output line,
it's more friendly for user to grep some time window from iostat log.

For basic stats:

./iostat -mt 1 sda sdb
Linux 5.15.0-97-generic (zwp-5820-Tower) 	09/29/25 	_x86_64_	(16 CPU)

09/29/25 15:22:03
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.83    0.00    1.56    0.47    0.00   97.14

Device             tps    MB_read/s    MB_wrtn/s    MB_dscd/s    MB_read    MB_wrtn    MB_dscd
sda              72.08         0.00         0.38         0.00       5060    2631239          0
sdb               0.00         0.00         0.00         0.00          0          0          0

./iostat -mT 1 sda sdb
Linux 5.15.0-97-generic (zwp-5820-Tower) 	09/29/25 	_x86_64_	(16 CPU)

Datetime          avg-cpu:  %user   %nice %system %iowait  %steal   %idle
09/29/25 15:22:19            0.83    0.00    1.56    0.47    0.00   97.14

Datetime          Device             tps    MB_read/s    MB_wrtn/s    MB_dscd/s    MB_read    MB_wrtn    MB_dscd
09/29/25 15:22:19 sda              72.08         0.00         0.38         0.00       5060    2631254          0
09/29/25 15:22:19 sdb               0.00         0.00         0.00         0.00          0          0          0

For extend stats:

./iostat -xmt 1 sda sdb
Linux 5.15.0-97-generic (zwp-5820-Tower) 	09/29/25 	_x86_64_	(16 CPU)

09/29/25 15:21:08
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.83    0.00    1.56    0.47    0.00   97.14

Device            r/s     rMB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wMB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dMB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.03      0.00     0.01  18.76   42.11    25.95   72.05      0.38    11.83  14.10    6.13     5.42    0.00      0.00     0.00   0.00    0.00     0.00    0.25   24.93    0.45   7.27
sdb              0.00      0.00     0.00   0.00    1.33     0.17    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00

./iostat -xmT 1 sda sdb
Linux 5.15.0-97-generic (zwp-5820-Tower) 	09/29/25 	_x86_64_	(16 CPU)

Datetime          avg-cpu:  %user   %nice %system %iowait  %steal   %idle
09/29/25 15:21:34            0.83    0.00    1.56    0.47    0.00   97.14

Datetime          Device            r/s     rMB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wMB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dMB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
09/29/25 15:21:34 sda              0.03      0.00     0.01  18.76   42.11    25.95   72.05      0.38    11.83  14.10    6.13     5.42    0.00      0.00     0.00   0.00    0.00     0.00    0.25   24.93    0.45   7.27
09/29/25 15:21:34 sdb              0.00      0.00     0.00   0.00    1.33     0.17    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00

Signed-off-by: zhangweiping <zhangweiping@didiglobal.com>