db must not use "Durable" and "SyncPeriod" in same time
txpool and downloader must be: Durable
nodedb: SafeNoSync+SyncPeriod
because txpool and downloader already can call sync when they need
(txpool after regular flush, downloader after piece download+validation
completion).
As per [EIP-1559](https://eips.ethereum.org/EIPS/eip-1559) , there is
only initial base fee after which it adjusts automatically. There are no
current references to a minimum protocol base fee on Ethereum, Gnosis or
Polygon.
The existing code would put a 7 wei minimum limit on transactions to be
included in the pool. This PR removes this check within txPool. Any
transaction can now be added to the `queued` sub-pool after which it
could get promoted to `pending` or `baseFee` subpools.
The`pricelimit` flag still exists and acts on non-local transactions as
a minimum feeCap for inclusion.
