Decrease additional cycles to 1

This MR aims to decrease the default number of additional cycles of history modes from 5 to 1. It means that then default behaviour of the node will be to keep 5 + 1 (as 5 cycles are always kept as the last allowed fork level is 5 cycle in the past), instead of 5 + 5.

Important notes

• This is not an issue for bakers. It may impact TRD users, but only the on doing late reward distributions. Maybe we should announce this in the baking slack #TRD channel(?)
• Users using the default full/rolling configuration will automatically switch to the "new default". Thus, they will transparently go from 5 to 1 cycle when restarting their node, without any notice.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR