Remove Bellatrix TTD logic

[zilm13]

After ethereum/execution-apis#570 is in effect, we will require to remove our logic which uses total difficulty when checking Bellatrix merge block. One of the solutions could be:

• hardcode terminal blocks for known networks:
  Hardcode Bellatrix Terminal Blocks for all known networks #8943
• make sure we handle response from EL without totalDifficulty without failure
• remove unnecessary Bellatrix TTD logic from codebase:
  Remove TTD Bellatrix merge configuration option #8951

[zilm13]

I think we can close this one as all of the parts are completed