This pull request introduces a new test suite in workload framework, for
transaction tracing.
**test generation**
`go run . tracegen --trace-tests trace-test.json http://host:8545`
and you can choose to store the trace result in a specific folder
`go run . tracegen --trace-tests trace-test.json --trace-output
./trace-result http://host:8545`
**test run**
`./workload test -run Trace/Transaction --trace-invalid ./trace-invalid
http://host:8545`
The mismatched trace result will be saved in the specific folder for
further investigation.
I added the history mode configuration in eth/ethconfig initially, since
it seemed like the logical place. But it turns out we need access to the
intended pruning setting at a deeper level, and it actually needs to be
integrated with the blockchain startup procedure.
With this change applied, if a node previously had its history pruned,
and is subsequently restarted **without** the `--history.chain
postmerge` flag, the `BlockChain` initialization code will now verify
the freezer tail against the known pruning point of the predefined
network and will restore pruning status. Note that this logic is quite
restrictive, we allow non-zero tail only for known networks, and only
for the specific pruning point that is defined.
