Merge #18982: wallet: Minimal fix to restore conflicted transaction notifications

7eaf86d3bf trivial: Suggested cleanups to surrounding code (Russell Yanofsky)
b604c5c8b5 wallet: Minimal fix to restore conflicted transaction notifications (Russell Yanofsky)

Pull request description:

  This fix is a based on the fix by Antoine Riard (ariard) in https://github.com/bitcoin/bitcoin/pull/18600.

  Unlike that PR, which implements some new behavior, this just restores previous wallet notification and status behavior for transactions removed from the mempool because they conflict with transactions in a block. The behavior was accidentally changed in two `CWallet::BlockConnected` updates: a31be09bfd and 7e89994133 from https://github.com/bitcoin/bitcoin/pull/16624, causing issue https://github.com/bitcoin/bitcoin/issues/18325.

  The change here could be improved and replaced with a more comprehensive cleanup, so it includes a detailed comment explaining future considerations.

  Fixes #18325

  Co-authored-by: Antoine Riard (ariard)

ACKs for top commit:
  jonatack:
    Re-ACK 7eaf86d3bf
  ariard:
    ACK 7eaf86d, reviewed, built and ran tests.
  MarcoFalke:
    ACK 7eaf86d3bf 🍡

Tree-SHA512: 9a1efe975969bb522a9dd73c41064a9348887cb67883cd92c6571fd2df4321b9f4568363891abdaae14a3b9b168ef8142e95c373fc04677e46289b251fb84689

doc/release-notes-18982.md

@@ -0,0 +1,8 @@
+Notification changes
+--------------------
+
+`-walletnotify` notifications are now sent for wallet transactions that are
+removed from the mempool because they conflict with a new block. These
+notifications were sent previously before the v0.19 release, but had been
+broken since that release (bug
+[#18325](https://github.com/bitcoin/bitcoin/issues/18325)).