Fix PV preview updates for matched image

[pford]

Description The PV preview for a matched image does not update when the PV cut is moved. The original PV request uses the matched image file_id but the cut region updates (SetRegion) use the reference file_id.

• What is implemented or fixed? Mention the linked issue(s), if any. Fixes #1304
• How does this PR solve the issue? Give a brief summary. The cut region's reference file_id is saved in PvCutParameters in addition to the file_id for the PV request. When SetRegion is sent, this reference file id is checked to see if an update should be generated.
• Are there any companion PRs (frontend, protobuf)? This issue is described in frontend #2240 but it is a backend fix only.
• Is there anything else that testers should know (e.g. exactly how to reproduce the issue)? See frontend issue; start a PV preview for a matched image and move the PV cut. The preview should update.

Checklist

• [x] changelog updated / ~no changelog update needed~
• [x] e2e test passing / corresponding fix added / new e2e test created
• [x] ~protobuf updated to the latest dev commit~ / no protobuf update needed
• [x] added reviewers and assignee
• [x] added ZenHub estimate, milestone, and release

[github-actions[bot]]

Package	Line Rate	Health
src.Cache	66%	➖
src.DataStream	52%	➖
src.FileList	67%	➖
src.Frame	50%	➖
src.HttpServer	42%	➖
src.ImageData	28%	❌
src.ImageFitter	89%	✔
src.ImageGenerators	43%	➖
src.ImageStats	76%	✔
src.Logger	44%	➖
src.Main	54%	➖
src.Region	18%	❌
src.Session	29%	❌
src.Table	52%	➖
src.ThreadingManager	87%	✔
src.Timer	85%	✔
src.Util	48%	➖
Summary	38% (7029 / 18596)	❌