Documentation: updates and fixes/review

[FedeMPouzols]

• The methods of ProcessingSet and MeasurementSetXds are now rendered
• ps_vis tutorial is updated to recent changes in nomenclature, the other (guides) notebooks are also updated
• various links are fixed to avoid absolute and/or local file links

About measurement_set_overview, I only made small or technical fixes. The few points about content that came to mind:

• In " data for a single observation, spectral window, polarization setup, observation mode, processor and beam per antenna" - should this also mention field (perhaps saying "typically" or similar)? Even though there is an exception, OTF, that is the default and by far the most common case I would expect.
• In Figure 1: "state_info" - is this new or being requested? Also, a bit further below in the table of MSv2=>MSv4 translation, state_info is listed as 'dataset' but it seems it would be a dict.
• Figure 2: this is now duplicated in the 'development' notebook (which perhaps could refer to this one).
• Perhaps, but not needed at this level of detail, where we say "table concept of rows has been replaced by relevant dimensions" => dimensions have replaced the concept of rows and also the dimensions of the "Format" column of the MSv2 tables, or dimensions of the corresponding casacore arrays for non-scalar data.

For the API fixes, I used the :members: directive. It seems we could also auto-generate everything as-is in the code using the extension 'sphinx.ext.autosummary'. Maybe we want to use that in the near future once the API is stable.
Note that I changed the top heading of measurement_set_api.rst to "Processing Set and Measurement Set API" as this made better sense to me considering what is included there, but please double-check.

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This contribution is made under the current ALMA software agreements. 
(c) European Southern Observatory, 2024 
Copyright by ESO (in the framework of the ALMA collaboration)