Use generated CUPS constants for destination and printer flags

[Abd002]

This PR replaces hard-coded CUPS destination/printer flag values with the constants generated from the local CUPS headers.

Previously, cups-rs used hard-coded values that matched older CUPS 2.x headers:

• DEST_FLAGS_MORE = 1
• DEST_FLAGS_REMOVED = 2
• PRINTER_DISCOVERED = 8

However, with CUPS 3 headers these values are different. For example, on my local CUPS 3 setup:

• DEST_FLAGS_MORE = 2
• DEST_FLAGS_REMOVED = 4
• PRINTER_DISCOVERED = 16777216

Because of this mismatch, cupsEnumDests() could return a destination with flags = 2, and cups-rs incorrectly treated it as REMOVED, causing valid printers such as PDF to be filtered out.