UpdraftPlus Premium

* FEATURE: Implement Backblaze Object Lock support (Premium version) * FIX: The email backup and basic report setting didn't work causing notification email confirming backup status couldn't be delivered to admin's email address (free version) * FIX: Fix WP-Optimize premium discovery for UpdraftCentral * FIX: Regression in 1.23.16 for correcting calls to translation functions which then caused some HTML attributes to be empty * FIX: Restoring backup sets via Migrate/Clone tab had caused all associated backup entities being downloaded immediately ignoring user preferences about the entities they wanted to restore * FIX: Third-party library conflict (phpseclib) with WP All Import Pro and AIO WP Migration plugins that caused failure in testing SFTP credentials and backing up to the SFTP remote storage * FIX: Restore compatibility with WordPress multisite running on versions < 4.9 caused by use of function not present before then * TWEAK: Add new translation entries for UpdraftCentral * TWEAK: Got rid of PHP 8.2 deprecation messages caused by a null value being passed to the htmlspecialchars() function and creation of dynamic property * TWEAK: Got rid of PHP 8.3 deprecation messages caused by calling get_class() without arguments. * TWEAK: Refactor methods in UpdraftPlus_Database_Utility class * TWEAK: Send an email if the backup directory is not writable. * TWEAK: Add and set the `filename_only` parameter to reduce search times when looking for specific backup files in Dropbox. * TWEAK: Autoload PHP secure communication library (phpseclib) in a better way that would prevent already-loaded phpseclib classes (by other plugin) from being used in certain operations * TWEAK: Add updraftplus_backup_db_header_append filter to allow site owners to include arbitrary content in their database backup header