Fix Stats information fails to load when date cannot be parsed when returned from API

[staskus]

Fixes #22859
WPKit-PR: wordpress-mobile/WordPressKit-iOS#771

All of the changes and explanations are within WPKit PR. In short, DateFormatter fails to convert a date string (2023-10-01) string to Date on rare occasions when DST happens on that particular date at midnight.

This PR also contains additional changes due to a state of WordPressKit and WordPressAuthenticator. I'll update WP-iOS PR once WPKit-iOS changes are merged.

To test:

The easiest way to reproduce and confirm that the issue is fixed is to follow the steps from #22859

1. Switch the time zone to Paraguay/Asuncion
2. Enable Stats Traffic feature flag
3. Open Stats Traffic tab
4. Select weeks
5. Come back to Sep 25 - Oct 1, 2023 week
6. Confirm data loads

Regression Notes

1. Potential unintended areas of impact

There shouldn't be any. WPKit-PR: wordpress-mobile/WordPressKit-iOS#771 adds unit tests to make sure that a new date formatter behaves in exact same way but additionally doesn't fail during DST changes.

2. What I did to test those areas of impact (or what existing automated tests I relied on)

Unit tests, manual tests

3. What automated tests I added (or what prevented me from doing so)

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr22910-46dd232
	Version	24.5
	Bundle ID	org.wordpress.alpha
	Commit	46dd232
	App Center Build	WPiOS - One-Offs #9323

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[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr22910-46dd232
	Version	24.5
	Bundle ID	com.jetpack.alpha
	Commit	46dd232
	App Center Build	jetpack-installable-builds #8367

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.