Make manually-named model fields more prominent in column picker

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**What problem will this feature request solve?**

A common use case is to build a Model for consumers to avoid doing manual joins, then renaming a column for clarity. For example, we can join the Orders and People tables, and rename the `Email` column to `User email`:

However, this name is not shown alone in the column picker for summarizing or filtering. It also shows the tables and columns where the data is coming from, which the model is supposed to hide/abstract away:

The column in the resulting table does have the correct name of `User email`:

**Describe the solution you'd like.**

In the column picker, show user-specified column names for models instead of table names with foreign key relationships. Disambiguate by showing the relationship only if it's necessary.

**How does this feature request impact you?**

Can be confusing for self-service users. The only workaround is to build the model with an equivalent database view.

Start at the column picker and trace how model fields are labeled for summarizing and filtering. Check how user-specified names and table or relationship names are supplied to that UI. Done means manually named model fields appear by their specified names, with relationship details shown only when needed to disambiguate.

Written by the indexing model from the issue text.