UI: Ember upgrade: Handle deprecation router service from host

[hellobontempo]

Description

Handles Use alias for inject router service from host application. This PR is based on initial work done by #28281, which I recommend comparing to the changes here.

In summary this PR:

• replaces router engine dependencies with aliased app-router
• call the alias @service('app-router') router within engines instead of @service router

Deviations from original PR:

The reason for this is based on the ember guides here:

• I decided to handle the transition-to slightly differently than the original PR and uninstalled ember-router-helpers and replaced it with a global transition-to helper that uses getOwner to dynamically determine which router to use.
• Similarly, I refactored LinkedBlock (which is a core component used across engines and the main app) to lookup the appropriate router service via a getter, which felt more stable instead of attempting to inject a service that doesn't exist (which according to above, would throw an error)

TODO only if you're a HashiCorp employee

• Backport Labels: If this PR is in the ENT repo and needs to be backported, backport
  to N, N-1, and N-2, using the backport/ent/x.x.x+ent labels. If this PR is in the CE repo, you should only backport to N, using the backport/x.x.x label, not the enterprise labels.
  • If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
  files.
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