Simplify Mounts

[mxkpp]

This removes some mounts that are no longer needed:

1. nwm-msw-mgr module parameter files are baked into that Python package's site-packages folder
2. ngen-forcing configuration files will be baked into that Python package's site-packages folder when this PR in that repo is merged: Include Forcing Config Files in Python Package ngen-forcing#166
3. There were some mounts that had 2 targets in case the flexibility was needed. I don't think users have been using that. Removing.
4. There were some mounts that were added to help with taking models originating from ngen-cerf cluster workflows and running them in the nwm-rte environment. This has not been used lately, and testers can now use nwm-rte to build realizations directly. Removing.

While NGWPC/ngen-forcing#166 has been merged into ngwpc-candidate, this PR should not be merged until the changes from that forcing PR have made it into development.

Edit: the above PR in ngen-forcing has been merged, so this can be merged any time.