EntityViewsData generates incorrect data for fields with multiple properties (address, price)

We need a Commerce-specific fix for this core issue #2337517: EntityViewsData does not handle main properties correctly.

Quoting myself from that issue:

The resulting views data is broken for:
1) Fields with no main property name
2) Fields with multiple properties whose main property is not the first one

What happens in case of #1 is that the first random property gets promoted to main, so it can't be used separately anymore.
For address fields this is the "langcode" field. For price fields this is the "number" field.
Instead, when the main property name is NULL, we should be adding a pseudo-field whose only purpose is to render the field.
That will keep access to the individual properties intact.

The other related problem is that mapSingleFieldViewsData() uses the "field" handler for every property, which results in the entire field being rendered, instead of just the individual property. We should be using the "standard" handler for non-main properties.

#5 we realized that we can't introduce the pseudo-field because the behavior change would represent too big of a backwards compatibility break. However, we can do the following:
1) Use the field's main property name, instead of always falling back to the first property. This fixes tax number fields, where the main property is value but the first property is type.
2) Fix views data to only use the "field" handler for the main property, not for all of them. This allows people to output just the currency code, for example.
And since we are already messing with the logic, we can make sure that each handler has a field_name defined, removing the workaround from processViewsDataForDatetime and others.