Brain atlas model for targeted structures

[saskiad]

Is your feature request related to a problem? Please describe.
Brain atlas has been added to the models, let's use it in the schema.

Describe the solution you'd like
Use the brain atlas model for targeted structures. In many places in procedures and session

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[dbirman]

If we update aind-data-schema-models to have enum classes based on Bruno's PR then this should wait on that