Misc cleanups of AST node API

- changed field names and a couple accessors to consistently use full words ("statement" instead of "stmt")

- applied several local analyzers (from IntelliJ) to remove redundant modifiers, unnecessary explicit types (yay Java 8), etc.

RELNOTES: None
PiperOrigin-RevId: 161551096
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
index f0cd551..fc5e586 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
@@ -523,7 +523,7 @@
     List<Statement> body = ((FunctionDefStatement) file.get(0)).getStatements();
     assertThat(body).hasSize(1);
 
-    List<Statement> loop = ((ForStatement) body.get(0)).block();
+    List<Statement> loop = ((ForStatement) body.get(0)).getBlock();
     assertThat(loop).hasSize(3);
 
     assertThat(((FlowStatement) loop.get(0)).getKind()).isEqualTo(FlowStatement.Kind.BREAK);