Merge #19090: refactor: Misc scheduler cleanups

fa8337fcdb clang-format scheduler (MarcoFalke)
fa3d41b5ab doc: Switch scheduler to doxygen comments (MarcoFalke)
fac43f9889 scheduler: Replace stop(true) with StopWhenDrained() (MarcoFalke)
fa9cca0550 doc: Remove unused documentation about unimplemented features (MarcoFalke)
fab2950d70 doc: Switch boost::thread to std::thread in scheduler (MarcoFalke)
fa9819695a test: Remove unused scheduler.h include from the common setup (MarcoFalke)
fa609c4f76 scheduler: Remove unused REVERSE_LOCK (MarcoFalke)

Pull request description:

  This accumulates a bunch of cleanup that was long overdue, but I haven't yet gotten around to address. Specifically, but not limited to:

  * Remove unused code, documentation and includes
  * Upgrade to doxygen documentation

  Please refer to the individual commits for more details.

ACKs for top commit:
  jnewbery:
    utACK fa8337fcdb

Tree-SHA512: 0c825ad9767e2697a3ef1ec1be13fdc2b18eeb7493ad0be5b65cc9f209391e78b17ee66e35e094c5e171c12b0f1624f287a110f6bddaf3024b708877afa8552e

src/test/scheduler_tests.cpp

@@ -89,7 +89,7 @@ BOOST_AUTO_TEST_CASE(manythreads)
     }
 
     // Drain the task queue then exit threads
-    microTasks.stop(true);
+    microTasks.StopWhenDrained();
     microThreads.join_all(); // ... wait until all the threads are done
 
     int counterSum = 0;
@@ -155,7 +155,7 @@ BOOST_AUTO_TEST_CASE(singlethreadedscheduler_ordered)
     }
 
     // finish up
-    scheduler.stop(true);
+    scheduler.StopWhenDrained();
     threads.join_all();
 
     BOOST_CHECK_EQUAL(counter1, 100);
@@ -186,7 +186,7 @@ BOOST_AUTO_TEST_CASE(mockforward)
     scheduler.MockForward(std::chrono::minutes{5});
 
     // ensure scheduler has chance to process all tasks queued for before 1 ms from now.
-    scheduler.scheduleFromNow([&scheduler] { scheduler.stop(false); }, std::chrono::milliseconds{1});
+    scheduler.scheduleFromNow([&scheduler] { scheduler.stop(); }, std::chrono::milliseconds{1});
     scheduler_thread.join();
 
     // check that the queue only has one job remaining