[TASK]: Reorganize confusing API routes

[mwdchang]

Some of our API route names are confusing and appear to clash with each other in terms of their functionality. We should take a resource-centric approach for REST APIs, see for example in https://restfulapi.net/resource-naming/

Rename/move

• GET /models/from-model-configuration/:model-config-id => GET /model-configurations/:id/original-model
• GET /model-configurations/as-configured-model/:config-id => GET /model-configurations/:id/model
• PUT /model-configurations/as-configured-model => Remove, doesn't seem to be in use
• POST /workflows/:id/node/:nodeId/selected-output/:outputId => POST /workflows/:id/node/:nodeId/output/:outputId