add dry runs methods to bump versions in order to better check if versions are successive

[MihaiTabara]

When we moved nightlies on ESR, there have been some nightly-version related operations that had to be ported in a bunch of places across our projects, including bouncerscript.

@JohanLorenzo and I agreed that some of the operations that were duplicated in here should be made more accessible in this module directly.

This is to track the move of the check_versions_are_successive function directly in this module.

Once that is added here, we should revisit bouncerscript logic as well to simplify it 👍

[MihaiTabara]

The methods we add in here should maybe handle ESR cuts as well, even if those happen every {7,8} releases. Otherwise, checks like this will fail.

[JohanLorenzo]

Done in #63 !