Updated default Dockerfile to handle newer PHP versions

[uberbrady]

Now that our minimum PHP version is higher than it used to be, the default Docker image needs to be updated accordingly. Since it looks like we need to use a later Ubuntu version to have access to newer PHP versions, I upgraded us to the latest LTS version of Ubuntu. Then I was able to install PHP8.3.

Additionally, it seems that now Ubuntu creates an Ubuntu user as userid=1000, which we were using for our own user previously. I instead shifted the UID of our created user to 10000, which, if we were using uid 1000 just for 'visibility' should also be pretty easy to visually distinguish. I'm not sure, though, if the uid of 1000 was used anywhere else in the system, and if we were, we should definitely change it there as well.

[what-the-diff]

PR Summary

• Updated Operating System
  The base operating system has been altered from Ubuntu version 22.04 to the newer version 24.04. This change ensures that our system is running on the most up-to-date and secure version of Ubuntu.

• PHP Version Upgrade
  We've done an upgrade from PHP 8.1 to PHP 8.3. In addition to this, we've updated all associated PHP packages. This ensures that we're using the most recent version, which usually has better performance, features, and enhanced security measures.

• Changed Encryption Extension Path
  Updating the mcrypt extension path to be in line with PHP 8.3, assures compatibility with the updated version.

• Modified PHP Configuration Paths
  The PHP configuration paths for variables_order have been adjusted to match the new PHP version. This alignment guarantees smooth functionality following the upgrade.

• Altered Docker User ID
  The user ID for the 'docker' user has been shifted from '1000' to '10000'. The update provides flexibility, reduces potential conflicts with local user IDs, and enhances security management.