Fix whitespace around inserted property initializer

Fixes microsoft#18741

Author: amcasey

src/services/codefixes/fixAddMissingMember.ts

@@ -112,11 +112,11 @@ namespace ts.codefix {
                     createIdentifier("undefined")));
 
                 const propertyInitializationChangeTracker = textChanges.ChangeTracker.fromContext(context);
-                propertyInitializationChangeTracker.insertNodeAt(
+                propertyInitializationChangeTracker.insertNodeBefore(
                     classDeclarationSourceFile,
-                    classConstructor.body.getEnd() - 1,
+                    classConstructor.body.getLastToken(),
                     propertyInitialization,
-                    { prefix: context.newLineCharacter, suffix: context.newLineCharacter });
+                    { suffix: context.newLineCharacter });
 
                 const initializeAction = {
                     description: formatStringFromArgs(getLocaleSpecificMessage(Diagnostics.Initialize_property_0_in_the_constructor), [tokenName]),

tests/cases/fourslash/codeFixAddMissingMember4.ts

@@ -15,12 +15,11 @@
 verify.codeFix({
     description: "Initialize property 'foo' in the constructor.",
     index: 0,
-    // TODO: GH#18741 and GH#18445
+    // TODO: GH#18445
     newFileContent: `class C {
     constructor() {
-    \r
-this.foo = undefined;\r
-}
+        this.foo = undefined;\r
+    }
     method() {
         this.foo === 10;
     }

tests/cases/fourslash/codeFixAddMissingMember6.ts

@@ -13,12 +13,11 @@
 verify.codeFix({
     description: "Initialize property 'foo' in the constructor.",
     index: 0,
-    // TODO: GH#18741 and GH#18445
+    // TODO: GH#18445
     newFileContent: `class C {
     constructor() {
-    \r
-this.foo = undefined;\r
-}
+        this.foo = undefined;\r
+    }
     prop = ()=>{ this.foo === 10 };
 }`
 });