Search score, not just staves for linked system elements

[miiizen]

Resolves: #19472
Resolves: #18231

When checking if an element had already been added to a staff which was being cloned, we were only checking staves with the same id. This was missing system elements, which frequently aren't on the same staff in parts as they are in the score.

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[DmitryArefiev]

Tested #19472 on Win10, Mac13.6, LinuxUbuntu 22.04 - FIXED