Switch to managing projection/column aliases via ISqlAliasManager as well

[roji]

#32785 redid table alias management, introducing a new "SQL alias manager" which is responsible for tracking which aliases are already in use in a query, and ensuring new ones are unique with respect to those. It also concentrates the actual logic of what table aliases look like (first char, lowercase) in a single place, so that this logic can be tweaked/overridden.

However, this didn't make any changes to projection (i.e. column) alias management - these are still hard-coded in various places. We should also refactor that logic into the new SQL manager.

/cc @maumar