Implement Model & API Types for Job messages.

[jmchilton]

By this I mean Job.job_messages in the model layer and the job_messages field in the API for Job responses (https://github.com/galaxyproject/galaxy/blob/dev/lib/galaxy/schema/jobs.py#L284).

I'm still working on doing the same for dataset source transform actions (#19666). The client models will cleanup at least one remaining Vue TSC error. I think model layer typing is probably good also - I found a fairly obscure and fairly serious issue in 24.2 with those models for transform actions.