Add ZeroBaseFeeMarket to support post-London free gas networks

[siladu]

Details on https://github.com/hyperledger/besu/issues/4061

This allows private networks already using London fee market to start using free gas. Previously, since https://github.com/hyperledger/besu/pull/4003, it was only possible to start a free gas London network from genesis.

It also fixes an issue where the 0 initial base fee can creep back up to non-zero when a block uses enough gas: https://github.com/hyperledger/besu/issues/4218

Documentation

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Changelog

• [x] I thought about the changelog and included a changelog update if required.