Fix issue when cannot write GRIB based array field to disk

[sandorkertesz]

When calling GribMetadata.override() with headers_only_clone=True a new GRIB handle is generated with all the data values (and some related information) removed. With this the resulting object can be significantly smaller, especially if the data section is large.

Unfortunately, using this technique resulted in problems when ArrayFields were derived from GRIB data. These fields contain a GribMetadata object created with calling GribMetadata.override(headers_only_clone=True) on the original GRIB metadata.

• Problem 1: for ArrayFields with GRIB1 reduced Gaussian grid e.g. to_numpy() fails
• Problem 2: ArrayFields cannot always be written to disk with save(), write() or GribOutput

As a temporary solution, this PR enforces the use of headers_only_clone=False in GribMetadata.override(). With this the problems above are fixed, but ArrayFields will use more memory than before.

The aim is to sort out the problems related to cloning GRIB handles with the headers only option (this possibly requires changes in ecCodes) and enable using headers_only_clone=True again.

[codecov-commenter]

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Additional details and impacted files

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