drop unnecessary load_schema statements

Before rails 7.2:
All of this data was set in `load_schema!` so we needed to ensure
the schema was loaded to access _virtual_includes or _virtual_arel.
Same may be the case for has_attribute?

After rails 7.2:
It may have always been the case, but at least for the rails methods
we do not need to ensure the schema is loaded.
For our 2 class level variables, we now load _virtual_arel without
load_schema. So there is no reason to wait for schema_load.

- virtual_attribute?:
  - has attribute loads the schema if necessary
  - column_for_attribute loads the schema if necessary
- attribute_supported_by_sql?
  - has_attribute loads the schema if necessary
  - virtual_attribute? loads the schema indirectly (by 2 internal methods)
  - _virtual_arel is populated on class load, not schema load
- virtual_includes
  - _virtual_includes is populated on class load, not schema load

Author: kbrock

lib/active_record/virtual_attributes.rb

@@ -72,7 +72,6 @@ def virtual_attribute(name, type, uses: nil, arel: nil, **options)
       #
 
       def virtual_attribute?(name)
-        load_schema
         has_attribute?(name) && (
           !respond_to?(:column_for_attribute) ||
           column_for_attribute(name).kind_of?(ActiveRecord::ConnectionAdapters::NullColumn)

lib/active_record/virtual_attributes/virtual_arel.rb

@@ -83,7 +83,6 @@ def arel_table
         # - it is an attribute that is non virtual
         # - it is an attribute that is virtual and has arel defined
         def attribute_supported_by_sql?(name)
-          load_schema
           try(:attribute_alias?, name) ||
             (has_attribute?(name) && (!virtual_attribute?(name) || !!_virtual_arel[name.to_s]))
         end

lib/active_record/virtual_attributes/virtual_includes.rb

@@ -18,7 +18,6 @@ module VirtualIncludes
 
       module ClassMethods
         def virtual_includes(name)
-          load_schema
           _virtual_includes[name.to_s]
         end