Migrate some tests to the new htmlRunner

Fix events.get_timeStamp (was events.get_timestamp, wrong casing).

Rename `newRunner` to `htmlRunner`.

move tests to src/tests (from src/browser/tests). src/runtime and possibly other
parts might want to have html tests too.

src/tests/browser.html

@@ -0,0 +1,5 @@
+<script src="testing.js"></script>
+<script id=intl>
+  // this will crash if ICU isn't properly configured / ininitialized
+  testing.expectEqual("[object Intl.DateTimeFormat]", new Intl.DateTimeFormat().toString());
+</script>