Drop iOS 14 Support: Update remaining UTType usages (#3)

[kean]

Related Issue #20860

Removes all the remaining deprecated UTType APIs.

Conversion TL;DR

• kUTTypePNG → UTType.png
• UTTypeEqual(lhs, rhs) → lhs == rhs
• UTTypeConformsTo(lhs, rhs) → lhs.conforms(to: rhs)
• UTTypeCopyPreferredTagWithClass(type as CFString, kUTTagClassFilenameExtension) → UTType(type)?.preferredFilenameExtension

To test:

Most of the changes are covered by the existing unit tests. The changes are one-to-one replacements from the deprecated to the new API. I tested them in a separate target, too, just to make sure they produced the same results.

Regression Notes

1. Potential unintended areas of impact: Media-related features
2. What I did to test those areas of impact (or what existing automated tests I relied on): manual tests and unit tests
3. What automated tests I added (or what prevented me from doing so): yes

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	pr20905-9f4a4c5
	Version	22.6
	Bundle ID	com.jetpack.alpha
	Commit	9f4a4c5
	App Center Build	jetpack-installable-builds #5068

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[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	pr20905-9f4a4c5
	Version	22.6
	Bundle ID	org.wordpress.alpha
	Commit	9f4a4c5
	App Center Build	WPiOS - One-Offs #6042

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