Optimization: don't add txn back to mempool after 10 invalidates
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 8d22041):
https://github.com/bitcoin/bitcoin/pull/15402/commits/8d220417cd7bc34464e28a4861a885193ec091c2
Optimization: don't add txn back to mempool after 10 invalidates
Depends on D4803
Test Plan:
ninja check-all
Reviewers: #bitcoin_abc, deadalnix, markblundeberg
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D4804