Integrate purger to node

- Common
	- Add `IdxNonce` type used to track nonces in accounts to invalidate
	  l2txs in the pool
- Config
	- Update coordinator config will all the new configuration parameters
	  used in the coordinator
- Coordinator
	- Introduce the `Purger` to track how often to purge and do the job when
	  needed according to a configuration.
	- Implement the methods to invalidate l2txs transactions due to l2txs
	  selection in batches.  For now these functions are not used in favour
	  of the `Purger` methods, which check ALL the l2txs in the pool.
	- Call Invalidation and Purging methods of the purger both when the
	  node is forging (in the pipeline when starting a new batch) and when
	  the node is not forging (in coordinator when being notified about a
	  new synced block)
- L2DB:
	- Implement `GetPendingUniqueFromIdxs` to get all the unique idxs from
	  pending transactions (used to get their nonces and then invalidate
	  txs)
	- Redo `CheckNonces` with a single SQL query and using `common.IdxNonce`
	  instead of `common.Account`
- StateDB:
	- Expose GetIdx to check errors when invalidating pool txs
- Synchronizer:
	- Test forged L1UserTxs processed by TxProcessor
	- Improve checks of Effective values
- TxSelector:
	- Expose the internal LocalStateDB in order to check account nonces in
	  the coordinator when not forging.

common/account.go

@@ -257,3 +257,9 @@ func AccountFromBytes(b [32 * NLeafElems]byte) (*Account, error) {
 	}
 	return &a, nil
 }
+
+// IdxNonce is a pair of Idx and Nonce representing an account
+type IdxNonce struct {
+	Idx   Idx   `db:"idx"`
+	Nonce Nonce `db:"nonce"`
+}