Rescope upload tree when there is only 1 tree in the upload plan

[sharadsw]

Fixes #5338

The upload tree wasn't being rescoped in cases where upload plan had only 1 tree, due to which upload would be scoped to the default tree of the collection which meant upload didn't work if the upload tree of the plan was not the same as the default tree

Checklist

• Self-review the PR after opening it to make sure the changes look good
  and self-explanatory (or properly documented)
• Add automated tests
• Add relevant issue to release milestone

Testing instructions

• Go to the workbench
• Create an upload plan with only 1 tree which isn't the original tree
• Verify upload works

[emenslin]

Testing instructions

• Go to the workbench
• Create an upload plan with only 1 tree which isn't the original tree
• Verify upload works

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Uploading to a tree that is not the original will not connect a new child to the root node.

Uploading to the original tree:

chrome_1Bw2Kk5Mc9.mp4

There is different behavior depending on if the first rank is enforced or not. The first rank should always be enforced but it is possible to uncheck 'is enforced' for the top rank therefore this issue should be fixed for both cases.

Uploading to a different tree with first rank not enforced:

chrome_QhzZ1cvlKm.mp4

Uploading to a different tree with first rank enforced:

chrome_b9QrT3gdes.mp4

db: https://kufish212-issue-5338.test.specifysystems.org/specify/

[sharadsw]

What should be the expected behavior in both cases? It should use the existing root?