[WIP] chore: upgrades to Ember 5.4

[Pixelik]

Chore

Upgrades to Ember 5.4

• makes the minimum amount of changes needed to make it Ember-5-compatible

Upgrades dependencies

Most notably:

• ember-concurrency from v0.8 to v3
• ember-concurrency-decorators from v0.5 to v2
• ember-resolver from v5 to v11

Removes dependencies

Most notably:

• ember-decorators (not needed in Ember 5)
• @ember/jquery (not needed)
• ember-cli-changelog (not compatible with Ember 5) ⚠️
• ember-cli-release (not compatible with Ember 5) ⚠️
• ember-cli-shims (not needed in Ember 5)
• ember-paper (not compatible with Ember 5) ⚠️
• ember-disable-prototype-extensions (removed by ember-cli-update)
• ember-export-application-global (removed by ember-cli-update)

Adds resolutions

In order to enforce Ember-5-compatible versions of various modules

Documentation

⚠️ deactivates documentation as it was using ember-paper which is not Ember-5-compatible

Deactivates release process

Making a release is no longer possible because the following modules had to be removed as they are not ember-5-compatible:

1. ember-cli-changelog
2. ember-cli-release

⚠️ As a result, the purpose of this PR is to have an Ember-5-compatible branch that works as expected & can be installed asap in an SPA that is on Ember 5. Once releasing & documentation (further refactoring will be required) is reinstated, a proper release could then also be made.