GH-685 New Defaults and Blockchain service URL check

[czarte]

Note

Switches default chain to base-mainnet, makes --blockchain-service-url effectively required (with limited exceptions), updates default RatePack values, and aligns code/tests/docs accordingly.

• Config/Defaults:
  • Set DEFAULT_CHAIN to Chain::BaseMainnet; update chain-specific directories, literals, and messages to base-mainnet.
  • Adjust error messages and expectations referencing chain name (e.g., web3 initializer panic, paths, descriptors).
• CLI/Validation & Help:
  • Enforce --blockchain-service-url presence during unprivileged parsing (exceptions: zero-hop, --fake-public-key, --crash-point).
  • Expand BLOCKCHAIN_SERVICE_HELP and add public Base Mainnet endpoints; update tests for new text.
• Rates:
  • Lower DEFAULT_RATE_PACK values; add high RatePack override in multinode test.
• Blockchain/Web3:
  • Update expected tx hashes in web3 batch tests.
• Tests/Fixtures:
  • Update numerous tests to pass --blockchain-service-url and to use base-mainnet paths/identifiers.
  • Align config dumper, setup reporter, bootstrapper, and node configurator tests with new defaults and requirements.

^{Written by Cursor Bugbot for commit 09b9baf. This will update automatically on new commits. Configure here.}

[dnwiebe]

Approved with review2 merged in.