Fix Duplicate Printer PPD and driver selection

[SinghCod3r]

Summary

Improve the Duplicate Printer workflow by opening the existing New Printer dialog instead of using a separate name-only dialog.

The duplicated printer now starts with its existing configuration and allows the user to review or modify the settings before creating the new queue.

Changes

• Open the existing New Printer / Describe Printer dialog when duplicating a printer.
• Preserve the original printer's:
  • Device URI
  • PPD/driver
  • Description
  • Location
  • Shared state
  • Discovered device identity
• Preserve the driverless recommendation for printers that support driverless printing.
• Avoid unnecessary PPD loading and driver matching when the original driver is retained.
• Allow users to explicitly choose a different driver through the existing driver-selection workflow.
• Show the existing inline loading spinner while the driver database is being loaded.
• Clean up driver-loading state when navigating back or cancelling.
• Keep class duplication and rename behavior unchanged.
• Keep the normal Add Printer workflow unchanged.
• Add regression tests covering duplicate initialization, PPD preservation, device identity, driver selection, and loading behavior.
• Handle PPD retrieval/parsing failures safely and clean up temporary PPD files.

User-visible behavior

Previously:

Right-click printer → Duplicate → enter a new name

Now:

Right-click printer
    → Duplicate
    → New Printer / Describe Printer
    → review or modify settings
    → optionally choose a different driver
    → create the new printer

This also provides a way to correct the selected driver when needed without affecting the original printer.

Testing

• pytest -q test_newprinter.py — 78 passed
• python3 -m py_compile newprinter.py system-config-printer.py — passed
• git diff --check — passed
• Manually verified the Duplicate Printer workflow in the GUI.