Add point to Grid/Mesh location method

[oehmke]

This was mentioned by Tom (@tclune) on the NASA call on 3/3/2026. They need a method that given a set of points will return a corresponding set of index locations and tiles in a Grid or the equivalent in a Mesh. They just need PET local information and it's ok if it returns not found if the location is on another PET. However, we could also have a flag that tells the method to do a global search.

[tclune]

Some partial thoughts here.

1. MAPL/GEOS generally assume that there is only 1 DE per PET. (I suspect this is also true of most ESMF users.) So you probably need the usual optional DE input argument that defaults to DE 0.
2. You could another argument: logical, optional, intent(out) :: found(:) that users could use to determine which points are in the local domain. When absent, you'd need to put some "illegal" value into the coordinate indices.
3. If someone wants the "global" option, then you probably have to have output arrays for tile and DE indices.