When changing a package version, update rather than replace the tree node

[drewnoakes]

The dependencies tree currently looks for the node to update based on its caption.

When we change a package MyPackage from version 1.0 to 2.0, the caption changes from MyPackage (1.0) to MyPackage (2.0).

The current code thinks these are different packages and therefore removes the old tree and attaches a new one. This has the effect of causing the package's node to collapse if it were expanded, which is annoying.

Note any change here will need a corresponding change on the NuGet.Client side, as that code doesn't currently update attached child nodes if the package's version changes.

[drewnoakes]

We should be able to identify the node via its browse object, which would give us the actual dependency ID, to make this unambiguous.

[drewnoakes]

Note any change here will need a corresponding change on the NuGet.Client side, as that code doesn't currently update attached child nodes if the package's version changes.

The NuGet portion of this fix is in NuGet/NuGet.Client#5146