Reduce object allocation while compiling

[ericproulx]

This PR reduces object allocation when compiling an api.

The function prepare_path was calling inheritable_setting.to_hash 2 times to just keep namespace_stackable and namespace_inheritable.

Current allocation / bytes

Total allocated: 62277446 bytes (334535 objects)
Total retained:  5954533 bytes (15516 objects)

Current allocation / types

allocated objects by class
-----------------------------------
    218676  Array
     89913  Hash

This PR allocation/bytes

Total allocated: 51007518 bytes (220812 objects)
Total retained:  5954325 bytes (15514 objects)

This PR allocation/types

allocated objects by class
-----------------------------------
    128512  Array
     66354  Hash

This PR also changes the following

• use include instead of .send(:include)
• create a helpers module only if a helper is defined otherwise it's nil
• Remove || {} in favor of handling nil cases in some options passed to middlewares.

[numbata]

Fantastic job 👍