details:
1. The check for cumulativeGasUsed + tx.gasLimit <= header.gasLimit
makes neither sense nor is it part of the Eip1559 specs. Nevertheless
a check tx.gasLimit <= header.gasLimit is added to satisfy some
unit test (see comments in validateTransaction() body.)
2. As a replacement check for the one removed in 1, a check for
cumulativeGasUsed + gasBurned <= header.gasLimit has been added
(see comments in processTransactionImpl() body.)
3. Prototypes for processTransaction() variants have been cleaned up and
commented.
why:
Detail 1. in particular produces an error for tightly packed blocks when
the last tx in the list has a generous gasLimit.