Add xESMF regridder

[bouweandela]

Description

Add xESMF regriding scheme for the regrid preprocessor.

Example usage in preprocessor in recipe:

regrid:
  target_grid: 1x1
  scheme:
    reference: esmvalcore.preprocessor.regrid_schemes:xESMF
    method: bilinear
    periodic: true

Link to documentation: https://esmvaltool--2433.org.readthedocs.build/projects/ESMValCore/en/2433/api/esmvalcore.regridding_schemes.html#esmvalcore.preprocessor.regrid_schemes.xESMF

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Checklist

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• [x] 🧪 The new functionality is relevant and scientifically sound
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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 26 lines in your changes are missing coverage. Please review.

Project coverage is 94.34%. Comparing base (2fc8761) to head (b639462).

Files	Patch %	Lines
esmvalcore/preprocessor/_regrid_xesmf.py	31.57%	26 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2433 +/- ## ========================================== - Coverage 94.51% 94.34% -0.17% ========================================== Files 246 247 +1 Lines 14023 14062 +39 ========================================== + Hits 13254 13267 +13 - Misses 769 795 +26 ```

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[flicj191]

message for myself @flicj191 as I want to try to use this regridder. let me know if you would like me to do anything