WIP: feat(common): introduce ls-routes

[Toxicable]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Feature

Continuation of #778

[Toxicable]

Blocked on not being able to test this due to

ReferenceError: HTTP_INTERCEPTORS is not defined

[CaerusKaru]

Closing for now. If it's needed in the future we can bring it back.

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