[Bookings] Update the path of the resources endpoint

[hichamboushaba]

Closes WOOMOB-1526

Description

This PR updates the path of the bookings resources endpoint to align with the last update woocommerce/woocommerce-bookings#4069.
I kept the table name BookingResource, if I knew about the plan to change the endpoint path I would have opted for a more specific name in the table, but now I prefer to avoid another DB migration, let me know what you think about this.

The PR also includes two minor improvements:

• Simplify the code of filters since customerId is not nullable anymore.
• Skips fetching the order when the booking#orderId is 0L

Steps to reproduce

1. Use a CIAB test with last bookings version (p1760617545633669-slack-C03L1NF1EA3)
2. After updating the plugin, use the plugin SQL Buddy to remove the the keys wc_bookings_version and wc_bookings_db_version options from the wp_options table.
3. Refresh the resources page in wp-admin.
4. Open a booking that has a linked resource, and confirm there are no errors.

Testing information

• Confirm resources are loaded correctly.

The tests that have been performed

The above.

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 23.5. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce-Wear Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce-Wear Android
	Platform	⌚️ Wear OS
	Flavor	Jalapeno
	Build Type	Debug
	Commit	2f6496e
	Direct Download	woocommerce-wear-prototype-build-pr14771-2f6496e.apk

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Commit	2f6496e
	Direct Download	woocommerce-prototype-build-pr14771-2f6496e.apk

[AdamGrzybkowski]