Fix column name for grouping custom fields in Views

[mglaman]

Overview

Fixes the column Views uses for grouping custom fields. It was defaulting to value, the default column name for fields.

Technical Details

Provides a wrapped base field definition class to always return proper column names for custom fields. Modifies a View plugin method which replaces the field definition class.

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Release notes snippet

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[mglaman]

Okay looks like legitimate errors after I fixed my typos. Will look at it today

[jackrabbithanna]

I had left this PR in one of my locals.

I observed that with this PR, adding a Civi custom field, that is in a Civi custom field group allowing multiple values, breaks the View.

I see errors like:
The view test_multi_civi_fields_view failed to load an entity of type civicrm_contact at row 1 for field multi_1_20