Enable history output "groups" for simplified history namelists

### What is the feature/what would you like to discuss?

In CAM, many fields are output automatically via the `add_default` method. However, this not only clutters the calling subroutine code, but also results in large amounts of fields being output by default, even though the person running the simulation has no attention of using them. However, assuming that all fields must be added individually can result in giant `user_nl_cam` files which can be hard to read and/or error-prone.

One way to work around this issue in CAM-SIMA is to create namelist "groups", for example all meteorological state variables, which if specified by the user in `user_nl_cam` will output every history field labeled as being within that group (for example `T`, `U`, `V`, `PMID`). This way model users can avoid having to specify large numbers of history fields manually, while also avoiding the situation of having many fields output by default, even when they are not needed.

### Is there anyone in particular you want to be part of this conversation?

_No response_

### Will this change (regression test) answers?

No

### Will you be implementing this enhancement yourself?

Any Software Engineer can do this