Migrated some more info schema tables to use views:
+ character_sets, removed annotations
+ collations, removed annotations
+ dynamic_policy, removed annotations
+ engines, removed annotations
+ show keys, information_schema.{referential_constraints,table_constraints,key_column_usage}, removed annotations

Other changes:
+ Modify emitter to support direct info schema statements (for debugging)
+ Modify the info schema gold generation to be alpha.  This completely breaks the upgrade.
+ Added some generator classes for the direct views.  Use them for the replacement info schema entries.
+ Add support for variables into the view defs.  These are used in the show commands to pass in
  the like expr, where exprs, also for scoping.
+ Added a custom show keys implementation to handle temporary tables.
+ Add a projection override in ProjectingExecutionStep, used in show commands.
+ Add support for merging order by clauses in the view transform.
+ Added a big test for column declarations.  Currently disabled.

This is a checkpoint commit.  Next up is reworking user_column.