Add metric for failed archiving with stale live trace

app/workers/ci/rescue_stale_live_trace_worker.rb

@@ -7,10 +7,13 @@ module Ci
       # Archive stale live traces which still resides in redis or database
       # This could happen when ArchiveTraceWorker sidekiq jobs were lost by receiving SIGKILL
       # More details in https://gitlab.com/gitlab-org/gitlab-ce/issues/36791
+      failed_archive_counter = Gitlab::Metrics.counter(:job_stale_live_trace_failed_archive_total, "Counter of failed archiving with stale live trace")
+
       Ci::Build.finished.with_live_trace.find_each(batch_size: 100) do |build|
         begin
           build.trace.archive!
         rescue => e
+          failed_archive_counter.increment
           Rails.logger.error "Failed to archive stale live trace. id: #{build.id} message: #{e.message}"
         end
       end