proto: switch to 4h cycle

What

Lowering the cycle length to 4h

Why

Improve staking UX

How

Update of protocols parameters at protocol stitching:

Change of period length:

• blocks_per_cycle

Ensuring constant period duration:

• cycles_per_voting_period
• delegate_parameters_activation_delay

Ensuring same number of nonce

• Blocks_per_commitment

Ensuring revelation time is sufficient and have a sensible value for VDF computation

• Nonce_revelation_threshold
• vdf_difficulty

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