Assert the specific type of event, not just the existence of any event.

Also remove a bunch of custom uses of EventCollector, and use the (already
existing) EventCollectionApparatus instead.

--
MOS_MIGRATED_REVID=106047665
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/ValidationTest.java b/src/test/java/com/google/devtools/build/lib/syntax/ValidationTest.java
index 5f9a712..0f74735 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/ValidationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/ValidationTest.java
@@ -291,7 +291,7 @@
     setFailFast(false);
     parseFile(
         "def GenerateMapNames():", "  a = 2", "  b = [3, 4]", "  if a not b:", "    print(a)");
-    assertContainsEvent("syntax error at 'b': expected in");
+    assertContainsError("syntax error at 'b': expected in");
     // Parser uses "$error" symbol for error recovery.
     // It should not be used in error messages.
     for (Event event : getEventCollector()) {
@@ -383,6 +383,6 @@
   private void checkError(String errorMsg, String... lines) {
     setFailFast(false);
     parseFile(lines);
-    assertContainsEvent(errorMsg);
+    assertContainsError(errorMsg);
   }
 }