Swap route settings.configure-secret-backend for nested edit and index route under secret.configuration

[Monkeychip]

• Enterprise test pass

Description

This PR moves the route vault.cluster.settings.confgure-secret-backend to vault.cluster.secrets.backend.configuration.edit. It has also been renamed to "configuration/edit(js/hbs)".

To keep the vault.cluster.secrets.backend.configuration route URL and behavior the same, I moved the code from vault/cluster./secrets/backend/configuration to vault/cluster/secrets/backend/configuration/index. This way I could render the edit route without using {{outlet}}}. If there's another way to do this, I'm all ears.

NO REDIRECT: We intentionally opted to not redirect if a user navigated to the old route. We could have either caught the old url in the page-error component, or kept the old route around and transitioned in a beforeModel hook. However, modifying a root component like page-error or keeping a legacy route around for a url that was not likely to be bookmarked seemed like too much code debt.

Why?

• The route FKA configure-secret-backend was responsible for configuring secret-engines, but was a child of vault.cluster.settings and not vault.cluster.secrets.backend. This made it difficult to access secret-engine things. You can see this struggle in how the route has to query all the secret engines and search for the type to see if the route should throw an error or proceed. However, if it was a child route of vault.cluster.secrets.backend it would already have access to the secret-engine model and would not need to query all them and then search through.
• IMO, it makes sense here (the old path override also seems to agree). I'm actually not sure why it was under settings at all other than mount-secret-backend is under settings and they're related. Though, I personally don't think mount-secret-backend should be under settings either 🥫🪱.
• This route is currently only used for two secret-engines: aws and ssh. It will be used for more and only get more complicated.

Notes

• I ONLY moved files in this PR. There is sooo much more I could do (glimmerize, refactor methods, address current bugs). But because this is a significant change (anything routing always is), I wanted to make it clear what was actually happening. Those TODOs are coming, but not in this PR.
• TLDR: I don't have to merge this. I can continue my WIF work without these changes, but it started to feel like I was pilling fresh food onto a dirty plate. I don't have the time to clean the whole kitchen, but maybe tidy up a bit?

[github-actions]

CI Results:
All Go tests succeeded! ✅

[github-actions]

Build Results:
All builds succeeded! ✅

[hashishaw]

Nice work, this change makes a lot of sense! I think there are some routing change process things to consider before we go ahead and ship this, so I'm holding off approval for now

[hashishaw]

Beautiful! 🚢