unit test deprecated platforms

[brodycj]

Platforms affected

all

Motivation and Context

From work on PRs #851 and #852, I think the code to show which platforms are deprecated is not so well covered by testing. The following possible code mutation does not seem to trigger any test failures:

--- a/src/cordova/platform/list.js
+++ b/src/cordova/platform/list.js
@@ -58,7 +58,7 @@ function addDeprecatedInformationToPlatforms (platformsList) {
         var platformKey = p.split(' ')[0]; // Remove Version Information
         // allow for 'unknown' platforms, which will not exist in platforms
         if ((platforms.info[platformKey] || {}).deprecated) {
-            p = p.concat(' ', '(deprecated)');
+            p = p.concat(' ', 'xxx');
         }
         return p;
     });

Description

Add spec/cordova/platform/listDeprecated.spec.js to test the output in case of any deprecated platforms.

Testing

The above mutation leads to failures in the new test cases.

Checklist

• [x] I've run the tests to see all new and existing tests pass
• [x] I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[brodycj]

Thanks to @NiklasMerz for the review.

FYI the new test code is based on spec/cordova/platform/list.spec.js. We could probably simplify and improve this test code some more someday in the future.