Add unit conversion to DU to recipes that use toz

[schlunma]

Description

Adapts recipes that use toz in light of ESMValGroup/ESMValCore#2509.

Requires

• Make derivation of total column ozone (toz) more flexible and add derivation of stratospheric and tropospheric column ozone ESMValCore#2509
• Use our own unit conversion function in our fixes ESMValCore#2560
• Perfmetrics recipe fails in multi model mean step ESMValCore#2559

Note: There are two example recipes that use toz for which we don't need to change anything since they don't have a diagnostic:

• https://github.com/ESMValGroup/ESMValTool/blob/main/esmvaltool/recipes/examples/recipe_check_obs.yml
• https://github.com/ESMValGroup/ESMValTool/blob/main/esmvaltool/recipes/examples/recipe_preprocessor_derive_test.yml

https://github.com/ESMValGroup/ESMValTool/blob/main/esmvaltool/recipes/examples/recipe_check_obs.yml

---

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

---

To help with the number of pull requests:

• 🙏 We kindly ask you to review two other open pull requests in this repository

[valeriupredoi]

Draft PR, Manu, I'll approve and merge once it's RfR )had a look at it already). Also, if we don't measure lengths in alligators, like Muricans do, am not letting this through 🐊 😁