Deprecate primary symbols in handler. All usages are safe to be dropped.

reactor/API/src/jetbrains/mps/logic/reactor/program/Handler.java

@@ -28,6 +28,7 @@ public abstract class Handler {
 
     public abstract String name();
 
+    @Deprecated
     public abstract Iterable<ConstraintSymbol> primarySymbols();
 
     public abstract Iterable<Rule> rules();

reactor/Test/test/TestMatcher.kt

@@ -184,13 +184,13 @@ class TestMatcher {
     @Test
     fun multipleHandlers() {
         programWithHandlers(
-            handler("handler1", listOf(ConstraintSymbol("foo", 0)),
+            handler("handler1", emptyList(),
                 rule("main1",
                     headKept(
                         constraint("foo")
                     ))
                 ),
-            handler("handler2", listOf(ConstraintSymbol("bar", 0)),
+            handler("handler2", emptyList(),
                 rule("main2",
                     headKept(
                         constraint("bar")