Add missing Ember 4 deprecations

[jenweber]

Ember 4 deprecations never made it into this app, but they were documented in the Ember Data source code. The task here is to add those docs into this app so that we have all the info someone needs in one place in order to navigate upgrades.

How to help:

• Start from this branch by bartocc: 📝 Add all 4.x ember-data deprecation pages #1319 That PR has the empty files for most of the deprecations that need to be added. Make new files as needed.
• Copy-paste in all deprecations you find at https://api.emberjs.com/ember-data/4.12/classes/CurrentDeprecations
• Check to see if any deprecations are missing. Cross reference with the contents of this PR Ember 5 release post ember-blog#1273