fix: respect local ethereum provider config

[Genmin]

What I changed

• Updated BaseEthereumConfig.local to merge configured ethereum.local values into the existing local-network defaults instead of always returning the hard-coded default provider.
• Added a regression test covering ethereum.local.default_provider while preserving local defaults such as gas_limit="max" and required_confirmations=0.

Why

networks.ethereum.local.default_provider can resolve from config, but project.config.ethereum.local.default_provider was still reporting the computed default (test) because the computed local config ignored the raw configured local section.

Validation

• uv run pytest tests/functional/test_config.py -k "ethereum_local_network_config or ethereum_network_configs or network_gas_limit_default"
• uv run ruff check src/ape_ethereum/ecosystem.py tests/functional/test_config.py
• Manual sanity check: EthereumConfig.model_validate({'local': {'default_provider': 'node'}}).local.default_provider == 'node' and EthereumConfig().local.default_provider == 'test'

Closes #2490

[Genmin]

Rebased onto current main and addressed the mypy failure by annotating configured_local in BaseEthereumConfig.local. The previous markdown formatting failure was on an unrelated docs file and is green on the rebased branch.\n\nLocal validation after the update:\n\n- uv run --group lint ruff check src/ape_ethereum/ecosystem.py tests/functional/test_config.py\n- uv run --group lint ruff format --check src/ape_ethereum/ecosystem.py tests/functional/test_config.py\n- uv run --group lint --group test mypy src/ape_ethereum/ecosystem.py\n- uv run --group lint mdformat --check .md docs/**/.md\n- uv run --group test pytest tests/functional/test_config.py -k ethereum_local_network_config

[github-actions]

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