Drop iOS 14 Support: Replace deprecated UTType APIs in Media

[kean]

Related Issue #20860

This is a straightforward change that replaces APIs deprecated in iOS 15 with their direct replacements.

To test:

My main way to test it was by writing unit tests (prior to making a change), but I also tested it by checking media uploads from the app.

• Create a post
• Upload image/video/document
• Verify that upload worked
• Set breakpoint in MediaService.swift line 648 and verify that remoteMedia.mimeType is set according to the uploaded file

Regression Notes

1. Potential unintended areas of impact: media uploads
2. What I did to test those areas of impact (or what existing automated tests I relied on): manual testing, automated testing
3. What automated tests I added (or what prevented me from doing so): every changes was covered by tests

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.

[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	pr20887-567e627
	Version	22.6
	Bundle ID	com.jetpack.alpha
	Commit	567e627
	App Center Build	jetpack-installable-builds #5035

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

[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	pr20887-567e627
	Version	22.6
	Bundle ID	org.wordpress.alpha
	Commit	567e627
	App Center Build	WPiOS - One-Offs #6009

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

[momo-ozawa]

Nice work, works as described!

[momo-ozawa]

@kean I made a new "Drop iOS 14 support" and applied it to all relevant PRs

[kean]

Thanks, appreciate it, @momo-ozawa!