Remove obsolete Core Data models

[kean]

Similarly to the work Woo Mobile has done, I suggest removing obsolete Core Data models.

The cut-off data is 2020-10-05 (version 99), which should be safe enough. The chances that there is someone with a five year old app is close to zero.

This change reduces the app size by ~6.4 MB (13.4 MB → 7.8 MB). It should also slightly reduce the compile time (minus 54K lines of Core Data XML that needs to be compiled to code).

I'm not aware of any negative side effects of removing models that are no longer used. The remaining migration tests guarantee that migrations for models after 100 still work.

[dangermattic]

	1 Warning
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

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	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	30348
	Version	PR #25124
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	Commit	1fdc749
	Installation URL	3r31kudq6lcko

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

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	30348
	Version	PR #25124
	Bundle ID	org.wordpress.alpha
	Commit	1fdc749
	Installation URL	20ssospft8vmo

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[kean]

Looks like I need to remove some obsolete tests as well.