Remove local copy of FindESMF.cmake and rename esmf target to ESMF::ESMF

[DusanJovic-NOAA]

Description

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this change.

This PR removes local copy of FindESMF.cmake and renames esmf target to ESMF::ESMF. ufs-weather-model now uses the FindESMF.cmake module provided by the ESMF library.

Fixes # (issue)

How Has This Been Tested?

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ufs-weather-model regression test has been run on Ursa and WCOSS2. No change in baselines is expected.

Checklist:

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• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[bensonr]

@DusanJovic-NOAA @jkbk2004 - if #386 is acceptable, we should consider bundling it in with this one.