inplace introduce: insert whitespace before template if needed (IDEA-87487)

java/java-tests/testData/refactoring/inplaceIntroduceField/templateAdjustment.java

@@ -0,0 +1,5 @@
+class Test {
+  int f(){
+    return<caret>-1;
+  }
+}

java/java-tests/testData/refactoring/inplaceIntroduceField/templateAdjustment_after.java

@@ -0,0 +1,9 @@
+class Test {
+
+    private int anInt;
+
+    int f(){
+        anInt = -1;
+        return anInt;
+  }
+}