Add unit test for FeaturedSummary sponsoredPodcasts

[bjtitus]

Adds a unit test for the sponsoredPodcasts sorting in FeaturedSummary.

Also adds an extension, XCTestCase.waitForCondition to asynchronously wait for a callback to complete.

A few things to note:

• This requires a network connection
• I couldn't figure out a good way to reproduce without repopulating the items twice. It doesn't happen every time but it happened a majority of the time for me.

To test

• 🟢 CI
• Run unit tests and make sure they pass

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger

[SergioEstevao]

Code looks good and tests work locally.
But I'm bit sceptical about the need of network to be able to run test. Can't we mock the network call? Aren't we running into the risk of test failure because CI connectivity issues?

[SergioEstevao]

Version 7.76 has now entered code-freeze, so the milestone of this PR has been updated to 7.77.

[SergioEstevao]

@bjtitus are you planning to udpate this one?