✨ Add option to choose between `git rebase` or `git merge`

**Is your feature request related to a problem? Please describe.**
Some repositories require linear history (i.e. no merge commits) but the default implementation of both `IGitFow.FinishHotfix` and `IGitFlow.FinishRelease` use `merge` commands. This causes commits / PRs to be rejected

**Describe the solution you'd like**
Add new setting` RequireLinearHistory` to make the pipeline choose between `rebase` or `merge which value should be :
- `true` : only perform `rebase` commands
- `false` : only perform `merge` commands

By default `RequireLinearHistory` will be `false`.

**Describe alternatives you've considered**
N/A

**Additional context**
Add any other context or screenshots about the feature request here.