[CLEANUP] Remove internal Ember.assign usage

[nlfurniss]

Note: This is intended to land in a version of Ember that does not support IE11.

There is no need to use the assign polyfill internally post-IE11 support. This PR:

• removes Ember.assign usage
• removes @babel/plugin-transform-object-assign

Edit: Oddly, the same test fails locally on master. In this branch the tests all pass in the browser, with the failure only occurring when run in the console

[rwjblue]

Due to some complications with 3.27's migration to use real modules (and the resulting massive number of deprecations being triggered) we are not 100% certain (yet) that 4.0 will be the version just after v3.28.

In order to move ahead with v4.0 cleanup efforts (like this one), I've pushed a new branch that can serve as the target for breaking change PR's: https://github.com/emberjs/ember.js/tree/v4-cleanup.

I've updated this PR to target that branch, can you rebase against that branch and push an update?

Expand for an example of the commands needed for that rebase.

# starting from this PR's branch

git fetch origin
git rebase origin/v4-cleanup

# fix any conflicts

# push the rebase
git push -f

Those steps should be roughly what you need, but might need some tweaks based on your local repository setup (e.g. if you don't use origin for the main emberjs/ember.js repo you might have to use another remote name there).

Thank you for helping us push things forward!

[rwjblue]

#19558 will remove IE11 from the browserstack job, that CI run will fail until the other PR lands.

[nlfurniss]

Due to some complications with 3.27's migration to use real modules (and the resulting massive number of deprecations being triggered) we are not 100% certain (yet) that 4.0 will be the version just after v3.28.

In order to move ahead with v4.0 cleanup efforts (like this one), I've pushed a new branch that can serve as the target for breaking change PR's: https://github.com/emberjs/ember.js/tree/v4-cleanup.

I've updated this PR to target that branch, can you rebase against that branch and push an update?

Expand for an example of the commands needed for that rebase.
Thank you for helping us push things forward!

All rebased and tests pass! 🟢

[rwjblue]

Thanks @nlfurniss!