Make last disconnected block BLOCK_FAILED_VALID, even when aborted
Summary:
This PR makes a number of improvements to the InvalidateBlock (invalidateblock RPC) and RewindBlockIndex functions, primarily around breaking up their long-term cs_main holding. In addition:
- They're made safely interruptible (bitcoind can be shutdown, and no progress in either will be lost, though if incomplete, invalidateblock won't continue after restart and will need to be called again)
- The validation queue is prevented from overflowing (meaning invalidateblock on a very old block will not drive bitcoind OOM) (see #14289).
- invalidateblock won't bother to move transactions back into the mempool after 10 blocks (optimization).
Partial Backport of Bitcoin Core PR15402 (commit 519b0bc):
https://github.com/bitcoin/bitcoin/pull/15402/commits/519b0bc5dc5155b6f7e2362c2105552bb7618ad0
Make last disconnected block BLOCK_FAILED_VALID, even when aborted
Depends on D4804
Test Plan:
ninja check-all
Reviewers: #bitcoin_abc, deadalnix, markblundeberg, Fabien
Reviewed By: #bitcoin_abc, deadalnix, markblundeberg
Differential Revision: https://reviews.bitcoinabc.org/D4929