Expose `NOMAD_ENVOY_ADMIN_ADDR_<service>` / `NOMAD_ENVOY_READY_ADDR_<service>` to all tasks in alloc

### Proposal

Expose `NOMAD_ENVOY_ADMIN_ADDR_` and `NOMAD_ENVOY_READY_ADDR_` to all tasks in alloc. Right now they are only exposed to the connect sidecar task.

### Use-cases

I'm currently dealing with https://github.com/hashicorp/nomad/issues/15709 and trying to implement the proposed workaround. (Adding a ephemeral prestart task that sleeps until envoy is ready).
The proposed workaround requires hardcoding the admin/ready ports to the job file. In my case, I don't know them in advance.
My task groups usually contain multiple tasks and multiple connect sidecar tasks. Some contain a dynamic number of tasks (using dynamic blocks).
So, I'm unable to predict which port is being used.

### Attempted Solutions

Start by tracing how Nomad injects Connect sidecar environment variables into allocation tasks, focusing on the existing NOMAD_ENVOY_ADMIN_ADDR_ and NOMAD_ENVOY_READY_ADDR_ handling. Verify the behavior with multiple tasks and sidecars, including dynamically defined tasks; done means every task in the allocation receives the appropriate variables without requiring hardcoded ports.

Written by the indexing model from the issue text.