Further to the move - the VirtualBranchesExt trait creates a dependency towards gitbutler-project. The gitubler-branch crate doesn't have such dependency so i deemed it undesirable to introduce it just for a convinience method.
(Separately added an extention in gitbutler-virtual-actions since it already depends on project and to create a smaller diff)
This type currently acts more or less like a command context that lives for the duration of the request. Regardless of if we wanna keep this pattern or not, separating it out helps us split up core
This protects us from cyclic dependencies. Unfortunatelly as part of this, i had to introduce the imp Project as trait implementations since now Project is foreign
