Revert "kafka: redefine fetch latency metric"

This reverts commit 44bde8d.

Will be replaced with 23.3 commit

src/v/kafka/server/handlers/fetch.cc

@@ -708,8 +708,6 @@ class fetch_worker {
         std::vector<read_result> read_results;
         // The total amount of bytes read across all results in `read_results`.
         size_t total_size;
-        // The time it took for the first `fetch_ntps_in_parallel` to complete
-        std::chrono::microseconds first_run_latency_result;
     };
 
     ss::future<worker_result> run() {
@@ -871,7 +869,6 @@ class fetch_worker {
 
     ss::future<worker_result> do_run() {
         bool first_run{true};
-        std::chrono::microseconds first_run_latency_result{0};
         // A map of indexes in `requests` to their corresponding index in
         // `_ctx.requests`.
         std::vector<size_t> requests_map;
@@ -898,21 +895,13 @@ class fetch_worker {
                   _completed_waiter_count.current());
             }
 
-            std::optional<op_context::latency_point> start_time;
-            if (first_run) {
-                start_time = op_context::latency_clock::now();
-            }
-
             auto q_results = co_await query_requests(std::move(requests));
             if (first_run) {
                 results = std::move(q_results.results);
                 total_size = q_results.total_size;
 
                 _last_visible_indexes = std::move(
                   q_results.last_visible_indexes);
-                first_run_latency_result
-                  = std::chrono::duration_cast<std::chrono::microseconds>(
-                    op_context::latency_clock::now() - *start_time);
             } else {
                 // Override the older results of the partitions with the newly
                 // queried results.
@@ -934,7 +923,6 @@ class fetch_worker {
                 co_return worker_result{
                   .read_results = std::move(results),
                   .total_size = total_size,
-                  .first_run_latency_result = first_run_latency_result,
                 };
             }
 
@@ -956,7 +944,6 @@ class fetch_worker {
                 co_return worker_result{
                   .read_results = std::move(results),
                   .total_size = total_size,
-                  .first_run_latency_result = first_run_latency_result,
                 };
             }
 
@@ -966,7 +953,6 @@ class fetch_worker {
                 co_return worker_result{
                   .read_results = std::move(results),
                   .total_size = total_size,
-                  .first_run_latency_result = first_run_latency_result,
                 };
             }
 
@@ -1162,9 +1148,6 @@ class nonpolling_fetch_plan_executor final : public fetch_plan_executor::impl {
           fetch.responses,
           fetch.start_time);
 
-        octx.rctx.probe().record_fetch_latency(
-          results.first_run_latency_result);
-
         _last_result_size[fetch.shard] = results.total_size;
         _completed_shard_fetches.push_back(std::move(fetch));
         _has_completed_shard_fetches.signal();