Add test support for intrinsic sized nodes (#1671)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1671

This diff adds support for intrinsic sizing in generated tests. This is done by importing a testing font called "Ahem" which, as used, has an exact width and height of 10px for each character. Support has been added for C++, Java, and Javascript generated tests.

Reviewed By: NickGerleman

Differential Revision: D58307002

fbshipit-source-id: e1dcc1e03310d35a32e0c70f71994880d8f7de55

tests/generated/YGAlignSelfTest.cpp

@@ -5,12 +5,13 @@
  * LICENSE file in the root directory of this source tree.
  *
  * clang-format off
- * @generated SignedSource<<aa02633e6618a216338b08979becc2d6>>
+ * @generated SignedSource<<cf8b648c6ae6d97a36bd33a03cd624e9>>
  * generated by gentest/gentest-driver.ts from gentest/fixtures/YGAlignSelfTest.html
  */
 
 #include <gtest/gtest.h>
 #include <yoga/Yoga.h>
+#include "../util/TestUtil.h"
 
 TEST(YogaTest, align_self_center) {
   const YGConfigRef config = YGConfigNew();