Data::Sah::Resolve provides resolve_schema. Sah schemas can be defined in terms
of other schemas as base. The resolving process follows the (outermost) base
schema until it finds a builtin type as the (innermost) base. It then returns a
hash result (a DefHash with v=2) containing the type as well other information
like the collected clause sets and others.

This routine performs the following steps:
1. Normalize the schema
   Unless schema_is_normalized option is true, in which case schema is assumed
   to be normalized already.
2. Check if the schema's type is a builtin type
   Currently this is done by checking if the module of the name
   Data::Sah::Type::<type> is loadable. If it is a builtin type then we are
   done.
3. Check if the schema's type is the name of another schema
   This is done by checking if Sah::Schema::<name> module exists and is
   loadable. If this is the case then we retrieve the base schema from the
   $schema variable in the Sah::Schema::<name> package and repeat the process
   while accumulating and/or merging the clause sets.
4. If schema's type is neither, we die.