This ensures that the filter bad transactions can use the same context
each time, so increases an account nonce in the first batch of
transactions is committed to the simulation just in case the same
account appears in the next batch of transactions.
Also makes use of the new txpool candidate functionality to ensure we're
getting fresh transactions each time.
Change from:
```
begin(TxNoSync)
exec new block, index nee data
do limited pruning
commit()
send notifications about new data arrival to other apps, they may start reading new data at this time (by new read transactions)
```
Change to:
```
begin(TxNoSync)
exec new block, index nee data
commit() // no fsync here
send notifications about new data arrival to other apps, they may start reading new data at this time (by new read transactions)
begin()
do pruning
commit() // fsync here
```
it allows notify earlier. Fsync (of all changes) on modern drives is
fast, but on cloud-drives it’s about 1sec in worst cases.
So there is an issue with tracing certain blocks/transactions on
Polygon, for example:
```
> '{"method": "trace_transaction","params":["0xb198d93f640343a98f90d93aa2b74b4fc5c64f3a649f1608d2bfd1004f9dee0e"],"id":1,"jsonrpc":"2.0"}'
```
gives the error `first run for txIndex 1 error: insufficient funds for
gas * price + value: address 0x10AD27A96CDBffC90ab3b83bF695911426A69f5E
have 16927727762862809 want 17594166808296934`
The reason is that this transaction is from the author of the block,
which doesn't have enough ETH to pay for the gas fee + tx value if he's
not the block author receiving transactions fees.
The issue is that currently the APIs are using `ethash.NewFaker()`
Engine for running traces, etc. which doesn't know how to get the author
for a specific block (which is consensus dependant); as it was noting in
several TODO comments.
The fix is to pass the Engine to the BaseAPI, which can then be used to
create the right Block Context. I chose to split the current Engine
interface in 2, with Reader and Writer, so that the BaseAPI only
receives the Reader one, which might be safer (even though it's only
used for getting the block Author).
