Ensure consistent download_dataset for Copernicus data

[simone-silvestri]

See the comment below:

The problem with Copernicus that I was hitting here, is that it can be downloaded in one file for all the dates or in different files for all the dates and the code does not enforce a unique way now, i.e. some methods assume we have only one file per Metadata while other methods (metadata_path in this case) assumes we have one file per date (i.e. one file per Metadatum). Here I am changing metadata_path to point to only one file per Metadata, however, I think it would be best to download one file per date so we can reuse downloaded files if we want to change the date. I will change the name of this PR to reflect this change.

[simone-silvestri]

The problem with Copernicus that I was hitting here, is that it can be downloaded in one file for all the dates or in different files for all the dates and the code does not enforce a unique way now, i.e. some methods assume we have only one file per Metadata while other methods (metadata_path in this case) assumes we have one file per date (i.e. one file per Metadatum).
here I am changing metadata_path to point to only one file per Metadata, however, I think it would be best to download one file per date so we can reuse downloaded files if we want to change the date.
I will change the name of this PR to reflect this change.

[codecov]

Codecov Report

Attention: Patch coverage is 12.50000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 14.51%. Comparing base (8c0bb84) to head (ecbd738).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
ext/ClimaOceanPythonCallExt.jl	14.28%	6 Missing ⚠️
src/DataWrangling/Copernicus/Copernicus.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #522      +/-   ##
==========================================
- Coverage   14.54%   14.51%   -0.04%     
==========================================
  Files          48       48              
  Lines        2763     2770       +7     
==========================================
  Hits          402      402              
- Misses       2361     2368       +7     

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[navidcy]

Metadata has 3 params, right?

[simone-silvestri]

Right, I am not sure they are all needed because this is just dispatch type. For example

const ECCOMetadata{D} = Metadata{<:SomeECCODataset, D}

[simone-silvestri]

We can merge this, then I'll add the extra parameter introduced in #489 everywhere.