There are some places that get `map<foo, bar>` and return it to the caller as `"key": string(foo), "value": string(bar)` json. For that there's `map_to_key_value()` helper in api.hh that re-formats the map into a vector of json elements and returns it, letting seastar json-ize that vector.
Recently in seastar there appeared stream_range_as_array() helper that helps streaming any range without converting it into intermediate collection. Some of the hottest users of `map_to_key_value()` had been converted, this PR converts few remainders and removes the helper in question to encourage further usage of the stream_range_as_array().
Code cleanup, not backporting
Closesscylladb/scylladb#28491
* github.com:scylladb/scylladb:
api: Remove map_to_key_value() helpers
api: Streamify view_build_statuses handler
api: Streamify few more storage_service/ handlers
api: Add map_to_json() helper
api: Coroutinize view_build_statuses handler
36167a155e