Magento 2.4.6 support

[jooname]

Has previous been merged to the dev branch of Custobar/magento2-plugin, but due to the changes in the way of making changes to the repository during the process, will now make a proper description of the changes that originally have also gone out to the dev branch. Now just targeting master for the proper release.

In short the aim is to have the module support Magento version 2.4.6.

Major changes related to this:

• Magento\Framework\HTTP\ZendClient has been dropped in 2.4.6, which has been used by this module. To still support 2.4.4 and 2.4.5 which still have the class available the usage has been refactored to support all of these three versions. Details about this can be checked from Model/CustobarApi/README.md
• Support for Magento versions older than 2.4.4 has been dropped as 2.4.4 is the oldest officially supported version by Adobe. This means we could get rid of the deprecated InstallSchema and UpgradeSchema usages and replace these with the db_schema.xml definitions. This is technically a breaking change according to semantic versioning, so this is the main reason I updated the version in the README to be 3.0.0.

Minor changes added alongside this:

• Brought test definitions up to date so that they can be run in the currently supported Magento test frameworks, for some reason this has been left out from earlier Magento version support changes
• Fixed several code sniffer related warnings to make sure that catching actual errors is easier. For example, lack of comments, non scoped constants etc.
• Fixed issue with order placement time not exporting with correct value to Custobar API
• Fixed issue with sku resolving not always working Commerce edition due to the row_id and entity_id differences

How we have tested the changes on our side:

• Integration tests have been run against clean installations of Magento 2.4.4, 2.4.5 and 2.4.6 and they all seem to pass
• All Magento Functional Testing Framework tests listed here have been run against clean installations of Magento 2.4.4, 2.4.5 and 2.4.6 and they all seem to pass: https://developer.adobe.com/commerce/marketplace/guides/sellers/mftf-magento/
• One of our internal QA engineers has checked module functionality and connections to Custobar API in Magento 2.4.6 environment and no issues were found

[samipel]

LGTM