Move StructureDefinitionPath to Diagnostics

[andrzejskowronski]

Context: https://firelyteam.slack.com/archives/C011XD1TKL0/p1760014836433879?thread_ts=1760000890.173109&cid=C011XD1TKL0

We already removed it from .Expression for Validator using SDK6, but there's also suggestion to move it out of Details.Code
Right now we set it in diagnostic only if the path contains Profiled type or Slice (HasDefinitionChoiceInformation), and always add a Details entry