Update schema tests for rails/rails#45908

After rails/rails#45908 we can no longer manipulate
the ar_schema_migrations table via the ActiveRecord::SchemaMigration class, go
through the default instance instead.

lib/active_record/connection_adapters/oracle_enhanced/schema_statements.rb

@@ -276,7 +276,7 @@ def drop_table(table_name, **options) # :nodoc:
         end
 
         def insert_versions_sql(versions) # :nodoc:
-          sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
+          sm_table = quote_table_name(ActiveRecord::Base.connection.schema_migration.table_name)
 
           if supports_multi_insert?
             versions.inject(+"INSERT ALL\n") { |sql, version|

spec/active_record/connection_adapters/oracle_enhanced/database_tasks_spec.rb

@@ -81,8 +81,8 @@ def fake_terminal(input)
     describe "structure" do
       let(:temp_file) { Tempfile.create(["oracle_enhanced", ".sql"]).path }
       before do
-        ActiveRecord::SchemaMigration.create_table
-        ActiveRecord::Base.connection.execute "INSERT INTO schema_migrations (version) VALUES ('20150101010000')"
+        ActiveRecord::Base.connection.schema_migration.create_table
+        ActiveRecord::Base.connection.schema_migration.create_version("20150101010000")
       end
 
       describe "structure_dump" do
@@ -109,7 +109,7 @@ def fake_terminal(input)
 
       after do
         File.unlink(temp_file)
-        ActiveRecord::SchemaMigration.drop_table
+        ActiveRecord::Base.connection.schema_migration.drop_table
       end
     end
 

spec/active_record/connection_adapters/oracle_enhanced/schema_statements_spec.rb

@@ -1228,7 +1228,7 @@ class << @conn
     before do
       @conn = ActiveRecord::Base.connection
 
-      ActiveRecord::SchemaMigration.create_table
+      ActiveRecord::Base.connection.schema_migration.create_table
     end
 
     context "multi insert is supported" do
@@ -1256,7 +1256,7 @@ class << @conn
     end
 
     after do
-      ActiveRecord::SchemaMigration.drop_table
+      ActiveRecord::Base.connection.schema_migration.drop_table
     end
   end
 end

spec/active_record/connection_adapters/oracle_enhanced/structure_dump_spec.rb

@@ -334,10 +334,9 @@ class ::TestPost < ActiveRecord::Base
     let(:dump) { ActiveRecord::Base.connection.dump_schema_information }
 
     before do
-      ActiveRecord::SchemaMigration.reset_table_name
-      ActiveRecord::SchemaMigration.create_table
+      ActiveRecord::Base.connection.schema_migration.create_table
       versions.each do |i|
-        ActiveRecord::SchemaMigration.create!(version: i)
+        ActiveRecord::Base.connection.schema_migration.create_version(i)
       end
     end
 
@@ -377,7 +376,7 @@ class ::TestPost < ActiveRecord::Base
     end
 
     after do
-      ActiveRecord::SchemaMigration.drop_table
+      ActiveRecord::Base.connection.schema_migration.drop_table
     end
   end