Incr engine: refine reexecution position for reactivated occurrences

In short, this change restricts information algo needs from journal.
It restricts how far invalidation stage goes into journal.
Previously it fed ExecQueue with position arbitrarily far in 'past',
whereas now it feeds the closest valid position (the 'present').

reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ConstraintsProcessing.kt

@@ -81,7 +81,7 @@ internal class ConstraintsProcessing(private var dispatchingFront: Dispatcher.Di
         val justificationRoots = mutableListOf<Justified>()
 
         val it = this.iterator()
-        var prevChunk = it.next() // skip initial chunk
+        var lastValidChunk = it.next() // skip initial chunk
 
         while (it.hasNext()) {
             val chunk = it.next()
@@ -118,11 +118,11 @@ internal class ConstraintsProcessing(private var dispatchingFront: Dispatcher.Di
                     //  all occurrences from the head are principal.
                     assert(chunk.match.allHeads().all { it.isPrincipal })
 
-                    execQueue.offerAll(prevChunk.toPos(), validOccs.asIterable())
+                    execQueue.offerAll(lastValidChunk.toPos(), validOccs.asIterable())
                 }
+            } else {
+                lastValidChunk = chunk
             }
-
-            prevChunk = chunk
         }
     }
 

reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ExecutionQueue.kt

@@ -128,9 +128,7 @@ internal class ExecutionQueue(
     fun offerAll(continueFromPos: MatchJournal.Pos, occs: Iterable<Occurrence>) =
         occs.forEach {
             journalIndex.activatingChunkOf(it)?.let { occChunk ->
-                // todo: ensure which is better
-//                 offer(continueFromPos, occChunk)
-                offer(occChunk.toPos(), occChunk)
+                 offer(continueFromPos, occChunk)
             }
         }