Storefront's adaptation of Zend Framework DB 1

Changes made vs the original zf1/zend-db package.

1. Minimum PHP version increased to 7.4
2. We only support:

• MySQL (via PDO and not mysqli)
• MsSQL
• PostgreSQL
• SQLite

3. Depencancies removed:

• Zend_Loader
• Zend_Registry

4. We improved the quoteInto() method
5. We improved the describeTable() method, so it returns the length for integer columns
6. Added function insertOnDuplicate()