Regridder unification tasks

[stephenworsley]

📰 Custom Issue

The work being done in #198 can be separated into different pull requests:

• [x] Create a single generic regridder class capable of regridding from any kind of grid/mesh to any other. Have all other regridders derive from this one. A consequence of this refactoring is that ESMFAreaWeighted and ESMFAreaweightedRegridder will be able to act as a replacement for MeshToGridESMFRegridder/GridToMeshESMFRegridder (along with the new ESMFBilinear class). MeshToGridESMFRegridder and GridToMeshESMFRegridder are likely to be deprecated after their functionality if fully replaced (they remain the only regridders able to be saved/loaded). (#198)
• [x] #318
• [ ] Refactor tests to better reflect the new locations of the code.
• [x] Add documentation describing the new regridders. (begun with #268)
• [x] Add support for mesh to mesh regridding. (#287 )
• [ ] Add deprecation warnings for MeshToGridESMFRegridder and GridToMeshESMFRegridder.

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[github-actions[bot]]

@SciTools-incubator/esmf-regrid-devs This issue is stale due to a lack of activity in the last 90 days. Remove stale label or comment, otherwise this issue will close automatically in 7 days time.

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@SciTools-incubator/esmf-regrid-devs This issue is stale due to a lack of activity in the last 180 days. Remove stale label or comment, otherwise this issue will close automatically in 14 days time.