Remove old file name from coreth #1253
Description
Much of the Firewood load test framework (especially @aaronbuchwald's S3 instances) store state in a poorly named spot (specifically ${chainDataDir}/firewood_state, with no suffix. This will become especially confusing once log files are added, so this is being changed to ${chainDataDir}/firewood.db. However, all the existing S3 instances must also be changed for this. #1204 initializes all new databases at the separate location, and if there is a file in the old location, it will be moved. This code should be removed once the S3 buckets are corrected.
Notably, this will not require a subnet-evm port, since the parallel version of #1204 doesn't need to include the movement code.