[api/feature] allow returning full struct from /{jobs,allocations,evaluations}

Hi,

Being able to request a full struct instead of stub from the API would help make nomad-ui more powerful and simple to develop.

Having a `?full=1` or similar query argument flipping the API response from a "digest" into a full detailed response with all information directly.

e.g. `/v1/jobs?full=1` would return `/v1/job/:id` data for each job

Start by locating the API entry points for /v1/jobs, /v1/allocations, and /v1/evaluations and reading how their current digest responses are built. Define the full=1 response behavior from the issue examples, then verify that each endpoint returns the corresponding detailed records while preserving the existing default response.

Written by the indexing model from the issue text.