fixed CanonicalReason::Assumed to check for direct anchor when no descendant exists

[AayushGupta56]

fixes #2088

Summary :- When a transaction is both in assume_canonical and has a direct anchor, it was incorrectly returned as ChainPosition::Unconfirmed. This fix adds a check for a direct anchor in the None descendant case, returning ChainPosition::Confirmed when an anchor exists.

[AayushGupta56]

@ValuedMammal can you please review this ?
Should I also add the testcase you mentioned in the issue?
Although the issue was already assigned to someone else but the was no activity on this issue since 2 weeks, so I gave it a try 😅.

[evanlinjin]

@AayushGupta56 thanks for the PR. Please add some tests!

[AayushGupta56]

@AayushGupta56 thanks for the PR. Please add some tests!

added a test in test_canonical_view.rs