Develop function to provide a summary of the data in the s2dv_cube

https://earth.bsc.es/gitlab/es/auto-s2s/-/blob/master/tools/data_summary.R was created for this purpose and is currently being used in the loading module. The main goal is to provide users with the information they need to make sure that the data that has been loaded coincides with what they requested in the recipe, and inform them of the data dimensions and any missing files.

This issue is to track further development of data_summary() such as features that should be added or improved.

Features to be implemented:

• Months that have been loaded
• Range of the dates that have been loaded
• Object dimensions
• Basic statistical summary of the data
• Missing files
• Number of NAs per time dimension and latitude/longitude dimensions
• Variables that have been loaded, along with their units

Other tasks:

• Profiling (see es/sunset#55 (closed))
• Adapt to cases where Compute() is used