Transaction and Block validation should be done through chain instance

[shuse2]

Description

Update Transaction struct Validate to be private, and add ValidateTransaction, ValidateBlock and ValidateGenesisBlock to the Chain struct.

Transaction and Block validation should depend on the configuration pass to the chain. MaxTransactionSize MaxTransactionsLength, and Transaction or Block struct doesn't hold those values

Acceptance Criteria

• Validate on struct is private
• Update the usage of Validate to consistently use method from Chain

Additional Information

• Related Add transaction size validation #25