Add priority/sorting for AgentTicketZoom MenuModules

[itweserems]

In the current (and probably all previous) Znuny version, the MenuModule entries for AgentTicketZoom are sorted by key-numbers of their SysConfig entries, e.g. "000-Back", "210-Print". In current dev code-branch this sorting happens in Kernel/Modules/AgentTicketZoom.pm, starting on: https://github.com/znuny/Znuny/blob/f28d711ba7ea24282e90ff91f5b19baefcefd7b5/Kernel/Modules/AgentTicketZoom.pm#L1233

This should instead be done by a priority config, as it is done for other menus within Znuny.

For example, admins should be able to change a "priority" value, e.g. for "Ticket::Frontend::MenuModule###000-Back" that defines it's menu position, compared to the priorities of other MenuModule items.

I am currently preparing an additional option per MenuModule where sorting of MenuModule items in AgentTicketZoom is not based on the SysConfig-key but a new "Priority" parameter instead.

[rkaldung]

@itweserems I labeled the issue/MR as verified to have it merged. It is be possible that one of the developers requests some changes.

[rkaldung]

Internal issue 1064

[dennykorsukewitz]

Fixed in 7.3.1. via 9429f60258630a9c4d99a7c324b874d6a0003eb6 6916e1cd03a5d473d09b1af65e7d3729153479f5 eadb305f427bfbe0cd7942f1f5f3697d5778ae67