Track worker concurrency using Redis hash - 2nd try

The application track worker counts using a Redis hash per Sidekiq worker.
The hash fields are contain information of the Sidekiq process id and thread id.
The application also does a periodic hash clean up during
ConcurrencyLimit::ResumeWorker crons.

The change is behind a sidekiq_concurrency_limit_optimized_count feature flag.

spec/support/sidekiq.rb

@@ -11,8 +11,13 @@ def gitlab_sidekiq_inline
     # see https://github.com/sidekiq/sidekiq/issues/6069
     Sidekiq::Testing.inline!
+    # Set a thread-local sidekiq capsule as it may be accessed in the
+    # Gitlab::SidekiqMiddleware::ConcurrencyLimit::WorkerExecutionTracker
+    Thread.current[:sidekiq_capsule] = Sidekiq::Capsule.new('test', Sidekiq.default_configuration)
+
     yield
   ensure
+    Thread.current[:sidekiq_capsule] = nil
     Sidekiq::Testing.fake! # fake is the default so we reset it to that
     redis_queues_cleanup!
     redis_queues_metadata_cleanup!

spec/workers/concerns/search/worker_spec.rb

@@ -24,6 +24,6 @@ def self.name
     limit = 55
     expect(Search).to receive(:default_concurrency_limit).and_return(limit)
-    expect(Gitlab::SidekiqMiddleware::ConcurrencyLimit::WorkersMap.limit_for(worker: worker_class)&.call).to eq(limit)
+    expect(Gitlab::SidekiqMiddleware::ConcurrencyLimit::WorkersMap.limit_for(worker: worker_class)).to eq(limit)
   end
 end