Annotate fewer extracted constants with types

Expose `isContextSensitive` from the checker and omit type annotations
for expressions for which it returns false.

src/services/refactors/extractSymbol.ts

@@ -1004,7 +1004,7 @@ namespace ts.refactor.extractSymbol {
         const localNameText = getUniqueName(isClassLike(scope) ? "newProperty" : "newLocal", file.text);
         const isJS = isInJavaScriptFile(scope);
 
-        const variableType = isJS
+        const variableType = isJS || !checker.isContextSensitive(node)
             ? undefined
             : checker.typeToTypeNode(checker.getContextualType(node), scope, NodeBuilderFlags.NoTruncation);