Add support for hard-deleting Git repos

[igoravl]

Presently, when deleting a Git repo with Remove-TfsGitRepository it's sent to a Recycle Bin. Should have an option to hard-delete it, similarly to Remove-TfsTeamProject.

Reference: https://learn.microsoft.com/en-us/rest/api/azure/devops/git/repositories/delete-repository-from-recycle-bin?view=azure-devops-rest-7.1