Conda support on activate_script

[cmrqs]

Is your feature request related to a problem? Please describe.
#9273 introduces venv support when submitting jobs to a queue using an activation script. It would be nice to support conda as well.

Describe the solution you'd like
Currently, the environment variable VIRTUAL_ENV is used to activate venv. A similar CONDA_ENV variable could be used for the same purpose for conda.

Describe alternatives you've considered
I could change the entire project to use venv as well, but it's impractical.

Additional context
Multiple virtual environments can't be active at once (e.g. venv and conda simultaneously). If both environment variables are set, one must take precedence over the other.