postfix completion: inplace introduce variable: ensure doc committed when handler is started inside writeAction

test: switch on inplace mode in tests
EA-86900 - RE: PostprocessReformattingAspect.beforeDocumentChanged

java/java-tests/testData/codeInsight/template/postfix/templates/var/anonymous.java

@@ -0,0 +1,7 @@
+public class Foo {
+    void m() {
+        foo(new Runnable() {public void run()}.var<caret>);
+    }
+
+    void foo(Runnable r) {}
+}