cli: add `alloc list` command to match API endpoint availability

The Nomad API supports [listing allocations](https://developer.hashicorp.com/nomad/api-docs/allocations#list-allocations) which can be useful for operators in many situations. The Nomad CLI should be enhanced to also support an `alloc list` command for completeness. In medium and large clusters, this output will be very long, therefore it probably makes sense to ensure filtering and pagination are supported in the initial release of this addition.

Start with the Nomad allocations API documentation linked in the issue and the CLI entry point for allocation commands. Define how `alloc list` should expose filtering and pagination for large clusters, then verify the command matches the API endpoint and handles the expected output.

Written by the indexing model from the issue text.