* Let Commit() return void
The boolean return value will loose its meaning in the next commit
* Implement 2-stage commits for CDBTransaction and CScopedDBTransaction
CDBTransaction is changed to allow CDBBatch, CDBWrapper and other
CDBTransactions as parent instead of just CDBWrapper. This in turn allows
to implement multi-staged commits in CEvoDB.
We now have the "current transaction" which is started and ended (commit
or rollback) for each call to Connect-/DisconnectBlock. When the current
transaction is committed, it moves its contents into the "root transaction"
instead of directly writing to CDBWrapper.
CommitRootTransaction() then handles the final commitment to CDBWrapper. It
is called at the same time when the chainstate is flushed to disk, which
guarantees consistency between chainstate and CEvoDB.
* Allow to efficiently move values into parent transactions to avoid copies
When CDBTransaction<CDBTransaction<...>>::Commit() is called, we can avoid
copying values from this transaction to the parent transaction and instead
pass values by rvalue and let the contents be moved.
* Revert "Force FlushStateToDisk on ConnectTip/DisconnectTip while not in IBD (#2560)"
This reverts commit 6dfceaba5a.
* Ensure EvoDB consistency by storing the best block hash
This approach is similar to the one used for chainstate currently.
Ensures that:
- nodes that upgraded after DIP3 has all the data processed correctly (they will crash and require reindex);
- evodb/ is removed when blocks/ is removed (otherwise sync will fail due to duplicate records).
* Implement CEvoDB::VerifyBestBlock/WriteBestBlock and call them from ConnectBlock/DisconnectBlock
* Fix walletbackup.py
