Do not attempt to cache orders during order creation

[jorgeatorres]

Submission Review Guidelines:

• I have followed the WooCommerce Contributing Guidelines and the WordPress Coding Standards.
• I have checked to ensure there aren't other open Pull Requests for the same update/change.
• I have reviewed my code for security best practices.
• Following the above guidelines will result in quick merges and clear and detailed feedback when appropriate.

Changes proposed in this Pull Request:

As described in #37568, during an order's save various hooks are fired, and after most are executed, the orders cache attempts to cache the order.
Thing is, if during the execution of any of those hooks, wc_get_order() gets called on that same order ID, we end up in a situation where the cache first obtained and saved a specific order class (during the wc_get_order() call) and then WC_Abstract_Order::save() overrides that with the generic WC_Order instance that initiated the save.

This PR attempts to fix this by preventing the cache logic in WC_Abstract_Order::save() from intervening when we're creating an order. During edits/updates, things should be safer, as we should already be working on an object of the correct type.

Closes #37568.

How to test the changes in this Pull Request:

Using the WooCommerce Testing Instructions Guide, include your detailed testing instructions:

1. Create a test file with the following contents.

   <?php
   add_action(
       'woocommerce_new_order',
       function( $order_id ) {
    	   // this makes the cache store a specific order class instance, but it's quickly replaced by a generic one
    	   // as we're in the middle of a save and this gets executed before the logic in WC_Abstract_Order.
    	   $order = wc_get_order( $order_id );
       }
   );
   
   $order = new \WC_Order();
   $order->save();
   
   $order = wc_get_order( $order->get_id() );
   var_dump( get_class( $order ) );

2. Confirm that, on trunk, it prints WC_Order.
3. Confirm that, on this branch, it prints Automattic\WooCommerce\Admin\Overrides\Order, which is the correct order type.

[github-actions]

Hi @vedanshujain,

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[github-actions]

Test Results Summary

Commit SHA: 817458a

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	0m 52s
E2E Tests	186	0	0	10	0	196	14m 35s

---

To view the full API test report, click here.
To view the full E2E test report, click here.
To view all test reports, visit the WooCommerce Test Reports Dashboard.

[vedanshujain]

LGTM!

[codecov]

Codecov Report

Merging #37569 (817458a) into trunk (2cd5cdc) will decrease coverage by 0.0%.
The diff coverage is 100.0%.

Additional details and impacted files

@@            Coverage Diff             @@
##             trunk   #37569     +/-   ##
==========================================
- Coverage     51.7%    51.7%   -0.0%     
  Complexity   17257    17257             
==========================================
  Files          429      429             
  Lines        79765    79765             
==========================================
- Hits         41202    41200      -2     
- Misses       38563    38565      +2     

Impacted Files	Coverage Δ
...ocommerce/includes/abstracts/abstract-wc-order.php	76.0% <100.0%> (ø)

... and 1 file with indirect coverage changes