Add option to plot time on x-axis in monitoring Hovmoeller plots

[FranziskaWinterstein]

Description

This adds the option in the monitor script multi_datasets to create the hovmoeller plot hovmoeller_time_vs_lat_or_lon such that time is on the x-axis, which is more intuitive for time vs latitude. The default is time on y-axis and lat/lon on x-axis.
The new orientation can be chosen by the following setting in the recipe:

        plots:
          hovmoeller_time_vs_lat_or_lon:
            time_on: x-axis

Checklist

It is the responsibility of the author to make sure the pull request is ready to review. The icons indicate whether the item will be subject to the 🛠 Technical or 🧪 Scientific review.

• 🛠 This pull request has a descriptive title
• 🛠 Code is written according to the code quality guidelines
• 🛠 Documentation is available
• 🛠 Tests run successfully
• 🛠 The list of authors is up to date
• 🛠 Any changed dependencies have been added or removed correctly
• 🛠 All checks below this pull request were successful

New or updated recipe/diagnostic

• 🧪 Recipe runs successfully
• 🧪 Recipe is well documented
• 🧪 Figure(s) and data look as expected from literature
• 🛠 Provenance information has been added

[schlunma]

Thanks @FranziskaWinterstein, this is almost ready. There is just a tiny issue with axis labels.

[FranziskaWinterstein]

Yes, thank you for spotting this. (y)

[schlunma]

I tested the new option with one dataset and also multiple datasets, works as expected. Thanks!!