use TripolarGrid and ConservativeRegridding for CMIP (to merge)

[juliasloan25]

Purpose

New version of TripolarGrid + ConservativeRegridding, to be merged this time.

Replaces #1840

To-do

• add a config option for the ocean grid to use (LatitudeLongitude grid [default] vs TripolarGrid); use conservative regridding only with the TripolarGrid
• update construct_remapper to be generic/construct the appropriate remapper for each case
• add remap! methods for the conservative and non-conservative cases
• add construct_remapper methods for both cases

Content

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