Rename disable_batching attribute to match its semantics

disable_batching was being set to true for the subselection, but that is
actually where we do batching on mutations, so enable_batching matches how
it is actually being used.

Also, I moved the attribute to the mutation execution strategy, since that
is the only place it is used.

Author: dylanahsmith

lib/graphql/batch/execution_strategy.rb

@@ -1,7 +1,5 @@
 module GraphQL::Batch
   class ExecutionStrategy < GraphQL::Query::SerialExecution
-    attr_accessor :disable_batching
-
     def execute(_, _, query)
       Promise.sync(as_promise_unless_resolved(super))
     rescue GraphQL::InvalidNullError => err

lib/graphql/batch/mutation_execution_strategy.rb

@@ -1,18 +1,20 @@
 module GraphQL::Batch
   class MutationExecutionStrategy < GraphQL::Batch::ExecutionStrategy
+    attr_accessor :enable_batching
+
     class FieldResolution < GraphQL::Batch::ExecutionStrategy::FieldResolution
       def get_finished_value(raw_value)
-        return super if execution_context.strategy.disable_batching
+        return super if execution_context.strategy.enable_batching
 
         raw_value = Promise.sync(raw_value)
 
-        execution_context.strategy.disable_batching = true
+        execution_context.strategy.enable_batching = true
         begin
           result = super(raw_value)
           GraphQL::Batch::Executor.current.wait_all
           result
         ensure
-          execution_context.strategy.disable_batching = false
+          execution_context.strategy.enable_batching = false
         end
       end
     end