Add segment average request time to csv

[klauspost]

Add average request time for every operation that ended in segment.

Example:

index	op	host	duration_s	objects_per_op	bytes	full_ops	partial_ops	ops_started	ops_ended	errors	mb_per_sec	ops_ended_per_sec	objs_per_sec	reqs_ended_avg_ms	start_time	end_time
0	DELETE		5	1	0	1063	3	1065	1064	0	0	212.8	213.0495901475193	19.8231139520677	2022-12-13 18:29:47.171164484 +0530 +0530	2022-12-13 18:29:52.171164484 +0530 +0530
1	DELETE		5	1	0	1063	9	1070	1065	0	0	213	213.27079393205017	19.643081027230057	2022-12-13 18:29:52.171164484 +0530 +0530	2022-12-13 18:29:57.171164484 +0530 +0530
2	DELETE		5	1	0	1044	9	1046	1051	0	0	210.2	209.7154819242158	20.08534205233112	2022-12-13 18:29:57.171164484 +0530 +0530	2022-12-13 18:30:02.171164484 +0530 +0530
3	DELETE		5	1	0	1066	5	1069	1068	0	0	213.6	213.9573178303453	19.66177282771537	2022-12-13 18:30:02.171164484 +0530 +0530	2022-12-13 18:30:07.171164484 +0530 +0530
4	DELETE		5	1	0	1058	6	1061	1061	0	0	212.2	211.97409918718319	19.934280667295006	2022-12-13 18:30:07.171164484 +0530 +0530	2022-12-13 18:30:12.171164484 +0530 +0530
5	DELETE		5	1	0	1052	6	1055	1055	0	0	211	211.08925306238802	19.995692337440758	2022-12-13 18:30:12.171164484 +0530 +0530	2022-12-13 18:30:17.171164484 +0530 +0530
6	DELETE		5	1	0	1049	8	1054	1052	0	0	210.4	210.4996067535266	20.122888835551308	2022-12-13 18:30:17.171164484 +0530 +0530	2022-12-13 18:30:22.171164484 +0530 +0530
7	DELETE		5	1	0	1050	10	1055	1055	0	0	211	211.37156305734698	19.77957469099529	2022-12-13 18:30:22.171164484 +0530 +0530	2022-12-13 18:30:27.171164484 +0530 +0530