feat(api): implement eth_baseFee JSON-RPC method

[wjmelements]

PR description

Adds nonstandard eth_baseFee rpc method.
This method is similar to eth_blobBaseFee, and is implemented in erigon and in some third party RPC providers.

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• Considered documentation and added the doc-change-required label to this PR if updates are required.
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• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• spotless: ./gradlew spotlessApply
• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests
• hive tests: Engine or other RPCs modified?

[macfarla]

@wjmelements is there a spec for this method? Also DCO check is failing, you need to add signoff to your git commits

[wjmelements]

@wjmelements is there a spec for this method?

No. I am simultaneously attempting to add it to execution-specs.

The several places that I have found it only disagree on how to handle pre-London return; nil is most popular, matching eth_blobBaseFee, but I have found one place (ethermint, aka cosmos evm) that returns 0 instead. 0 would have been my choice but I didn't invent this method.