Enhance db:schema:dump with custom tasks

Rails 6.1 deprecates db:structure:* tasks in favor of db:schema:*
Let's create duplicates for now
When we migrate to Rails 6.1, we can remove the duplicates

lib/tasks/gitlab/db.rake

@@ -129,16 +129,31 @@ namespace :gitlab do
     end
     # Inform Rake that custom tasks should be run every time rake db:structure:dump is run
+    #
+    # Rails 6.1 deprecates db:structure:dump in favor of db:schema:dump
     Rake::Task['db:structure:dump'].enhance do
       Rake::Task['gitlab:db:clean_structure_sql'].invoke
       Rake::Task['gitlab:db:dump_custom_structure'].invoke
     end
+    # Inform Rake that custom tasks should be run every time rake db:schema:dump is run
+    Rake::Task['db:schema:dump'].enhance do
+      Rake::Task['gitlab:db:clean_structure_sql'].invoke
+      Rake::Task['gitlab:db:dump_custom_structure'].invoke
+    end
+
     # Inform Rake that custom tasks should be run every time rake db:structure:load is run
+    #
+    # Rails 6.1 deprecates db:structure:load in favor of db:schema:load
     Rake::Task['db:structure:load'].enhance do
       Rake::Task['gitlab:db:load_custom_structure'].invoke
     end
+    # Inform Rake that custom tasks should be run every time rake db:schema:load is run
+    Rake::Task['db:schema:load'].enhance do
+      Rake::Task['gitlab:db:load_custom_structure'].invoke
+    end
+
     desc 'Create missing dynamic database partitions'
     task :create_dynamic_partitions do
       Gitlab::Database::Partitioning::PartitionCreator.new.create_partitions
@@ -159,10 +174,16 @@ namespace :gitlab do
     #
     # Other than that it's helpful to create partitions early when bootstrapping
     # a new installation.
+    #
+    # Rails 6.1 deprecates db:structure:load in favor of db:schema:load
     Rake::Task['db:structure:load'].enhance do
       Rake::Task['gitlab:db:create_dynamic_partitions'].invoke
     end
+    Rake::Task['db:schema:load'].enhance do
+      Rake::Task['gitlab:db:create_dynamic_partitions'].invoke
+    end
+
     # During testing, db:test:load restores the database schema from scratch
     # which does not include dynamic partitions. We cannot rely on application
     # initializers here as the application can continue to run while