fix: propose gas limit validation

[mfrankovi]

• Allow setting propose gas limits in config file as hex by modifying getConfigDataAsUInt to accept hex strings
• Remove validation of propose gas limits from FullNodeConfig::validate since the validation depends if over the cornus HF. Add validation in DagBlockProposer constructor by reducing the value to the maximum gas limit allowed

[taraxadeploy]

prnet cleaned-up successfully