MDL-80669 reportbuilder: improved reporting of custom/profile fields.
Make the display of both custom and user profile fields consistent in
column callbacks. The defaults for each should be considered when both
rendering the column data and also when aggregating them (specifically
for numeric columns to ensure calculations are accurate).
When such fields are filtered, and they have user defined default
values then we should also take that into account to ensure that the
same values rendered in columns can always be filtered for.
During this change, I've updated some of the variables to improve
readability and future maintainability of these classes. Annoyingly
there are a non-zero number of changes just for Oracle support.
