search: add json-progress flag, to allow easy collection of metadata

[brads-au]

Added the --json-progress flag to the search options, as it can be useful to get just the search metadata (time, work, bps, eps) to analyse, or feed back into LogScale.

./humioctl search humio "* | count()" --start "30d" --json-progress
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":0,"workDone":0,"timeMillis":1,"epsValue":0,"bpsValue":0,"eventCount":0,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":0,"workDone":0,"timeMillis":1,"epsValue":0,"bpsValue":0,"eventCount":0,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":135,"workDone":95,"timeMillis":316,"epsValue":5698933.544303797,"bpsValue":3641665379.746835,"eventCount":1800863,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":135,"workDone":95,"timeMillis":316,"epsValue":5698933.544303797,"bpsValue":3641665379.746835,"eventCount":1800863,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":135,"workDone":108,"timeMillis":1318,"epsValue":6642142.640364188,"bpsValue":3158683620.637329,"eventCount":8754344,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":135,"workDone":108,"timeMillis":1318,"epsValue":6642142.640364188,"bpsValue":3158683620.637329,"eventCount":8754344,"done":false}
{"startMillis":1684743601339,"repo":"humio","queryString":"* | count()","totalWork":135,"workDone":135,"timeMillis":3210,"epsValue":7202546.105919003,"bpsValue":3546733072.8971963,"eventCount":23120173,"done":true}