[core] enforce claiming maximum coinbase amount [needs an HF]

[sumogr]

Ref Monero # 6760 adjusted for sumo

Quote Claiming a slightly lesser amount does not yield the size gains that were seen pre rct, so this closes a fingerprinting vector Unquote

This will need a hardfork, it can be on the same HF as CLSAG. Version number (10) and alias has been defined in cryptonote_config, no height entered till we decide