Append graffiti should be able to add clients info when only 4 bytes are available

[zilm13]

Description

With #8107 and #8175 we have added a feature to append CL and EL clients info to the graffiti when producing the block. Current minimal requirements are 5 bytes: <SPACE> + <CL CODE> + <EL CODE>. It would be good to keep this option available but also add 4 bytes option without a space, so users could utilize 28 bytes for their own graffiti while still be able to share clients info.