[452] A default multi-stream configuration

[tjhunter]

Description

Provides a default multi-stream configuration. Tested on leonardo with the command:

./hpc/launch-slurm.py --slurm-script ./hpc/leonardo/ecmwf/weathergen_slurm.sh --config config/mixed.yml

Note that it moves the irrelevant streams to streams_mixed_experimental.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Issue Number

Closes #452

Code Compatibility

• I have performed a self-review of my code