consul: include Nomad node ID in Consul token login metadata

[emmayusufu]

Consul tokens issued by Nomad via workload identity login carry a requested_by meta value (for example nomad_task_<name>), but nothing identifies which Nomad client issued the token. This adds the issuing client's node ID to the login request metadata, so a token can be traced back to the node that created it.

As @jrasell noted on the issue, the token created via login prefix in the description is controlled by Consul, not Nomad, so the node ID goes into the meta (the part Nomad controls). The description then reads:

token created via login: {"node_id":"<node-id>","requested_by":"nomad_task_<name>"}

Changes:

• Add node_id (from alloc.NodeID) to the Consul JWT login meta for both task and service tokens.
• Record login requests in the test Consul mock and assert the node ID is passed through.
• Changelog entry.

Fixes #28048

[hashicorp-cla-app]

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