Because we page headers contain the page->type as part of the header it is important we don't change the values we write other page->types as or we will create downgrade concerns. For this reason we can't remove WT_PAGE_COL_FIX from the type options but instead we rename it to something that indicates it is no longer used. 

This change may introduce some more instances of WT_ERR(__wt_illegal_value(session, page->type)); to various switch / case statements in the codebase.

Scope:

• Remove all references in the codebase to the former name of the macro value. This change will have cascading effects so expect the final changeset to be reasonably large. Try and commit it piecewise, e.g. a file or subset of files at a time.
• Rename the former to the latter.

Do this after WT-15869.