Use Folders for Classes

[jkmassel]

Removes most of the code from the Xcode project file, instead using a folder.

This makes the file way smaller, should make Xcode way more responsive, and should mean we get far fewer conflicts in the project file.

Uses @mokagio's idea from #23679 to make it CocoaPods-compatible.

To Test:

1. Ensure CI passes
2. Ensure that running bundle exec pod install locally works

[dangermattic]

	2 Warnings
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.
⚠️	This PR is assigned to the milestone 25.5. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

Generated by 🚫 Danger

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	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23736-a923946
	Version	25.4.2
	Bundle ID	org.wordpress.alpha
	Commit	a923946
	App Center Build	WPiOS - One-Offs #10919

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📲 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	pr23736-a923946
	Version	25.4.2
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	Commit	a923946
	App Center Build	jetpack-installable-builds #9959

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[crazytonyli]

😍

[kean]

Nice