Remove `escapeExpression` from `@ember/template`

[NullVoxPopuli]

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Co-Authored-By: @chriskrycho

Rebase of: https://github.com/emberjs/ember.js/pull/20360

This also gets a mention here: https://github.com/emberjs/rfcs/pull/1003 :sweat_smile: (for migration docs)

[kategengler]

If it was private, shouldn't need to be in the RFC, I'd think

[kategengler]

May have been private but Handlebars.Utils.escapeExpression has uses in addons...

[NullVoxPopuli]

May have been private but Handlebars.Utils.escapeExpression has uses in addons...

people using private apis should be used to what happens? :sweat_smile: :upside_down_face:

idk, what's the process here? do we need a deprecation in this case?

[kategengler]

Do they know it is private if it is hanging out on Ember.Handlebars.Utils.escapeExpression?

If it is truly private, we need an intimate API deprecation (1 LTS cycle), but if it is public, we need an RFC + full deprecation.

[bertdeblock]

I know ember-intl uses it as well.

[NullVoxPopuli]

I've now rebased this PR, as I forgot about it :sweat_smile:

[kategengler]

Some test failures