[C2] Install error on ticket_priority.code

[ywarnier]

This issue is entirely caused by this change (by me) 6524843#diff-69b0f41ba2dd4233930aef7512942159eeb80babc16c0c0afca02eb20adb22c0R26-R40 when I changed the string code of priorities (which I thought was unused) by an integer value. The DataFixture code is causing issues because it tries to use the constants (now numerical) to feed to setCode(), which expects a string.
I still think we can get rid of the string "code", but I think the installer (fixtures) use it to set a "title" that is translated, without relying on the integer ID which is not guaranteed (because auto-incremented) to be as specified in the constants.

If possible, remove the ticket_priority.code usage completely (find a way to remove its use in the fixtures) or, maybe more simply, return back to using letter codes in the tickets system (revert part of my commit above).

[christianbeeznest]

Fixed: we kept numeric PRIORITY_/STATUS_ constants and unblocked the installer. Entities now accept string|int in setCode() (cast to string) and fixtures call setCode((string)$code). Also aligned SQL updates to numeric IDs and unified the “Closed” constant usage. No schema changes.

f951466#diff-521b42ad1843e1244ce1c57f551760b036881bd3b60987713cf36e536e7aac6d

[ywarnier]

Thanks.