[3.13] gh-117398: Use the correct module loader for iOS in datetime CAPI test (GH-120477)

[neonene]

#119604 added a CAPI test for subinterpreters in the datetime tests; however, the test uses the ExtensionFileLoader to load _testcapi. iOS requires the use of the AppleFrameworkLoader.

(backported from commit 5c58e72, AKA gh-120477)

• Issue: Isolate the _datetime extension module #117398

[bedevere-bot]

You don't have write permissions to trigger a build

[neonene]

@freakboy3742 Could you review the backport? I failed to trigger the iOS build bot.

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 987dd52 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[freakboy3742]

@neonene Thanks for the backport (and nice work hunting down the fix without access to the buildbot!)