moving VVEL or WVEL to daily stream leads to model crash when monthly tavg files written

Description of the issue:

Reported on [DiscussCESM Forum](https://bb.cgd.ucar.edu/cesm/threads/an-error-is-reported-when-bhist-outputs-ocean-daily-data.7102/) by user [ZhangZJ](https://bb.cgd.ucar.edu/cesm/members/zhangzj.6547/).

Moving `VVEL` or `WVEL` to daily stream leads to model crash in `tavg_write_vars_nstd_ccsm`. The problem is hard-coded indices in 2nd dimension of `io_dims_nstd_ccsm`.

Version:
- CESM: 2.2, 2.1, 2.0, 1.2, 1.1, 1.0

Machine/Environment Description:
cheyenne

Any xml/namelist changes or SourceMods:
Copy `gx1v7_tavg_contents` into SourceMods/src.pop and change stream of `VVEL` or `WVEL` from 1 to 2.

Fix is to replace hardcoded indices in 2nd dimension of `io_dims_nstd_ccsm` with `tavg_MOC`, `tavg_N_HEAT`, or `tavg_N_SALT`, depending on which variable is being written. User confirms that this fixes problem on their platform.