Merge #18807: [doc / test / mempool] unbroadcast follow-ups

9e1cb1adf1 [trivial/doc] Fix comment type (Amiti Uttarwar)
8f30260a67 [doc] Update unbroadcast description in RPC results (Amiti Uttarwar)
750456d6f2 [trivial] Remove misleading 'const' (Amiti Uttarwar)
fa32e676e5 [test] Manage node connections better in mempool persist test (Amiti Uttarwar)
1f94bb0c74 [doc] Provide rationale for randomization in scheduling. (Amiti Uttarwar)
9c8a55d9cb [mempool] Don't throw expected error message when upgrading (Amiti Uttarwar)
ba54983182 [test] Test that wallet transactions aren't rebroadcast before 12 hours (Amiti Uttarwar)
00d44a534b [test] P2P connection behavior should meet expectations (Amiti Uttarwar)
bd093ca15d [test] updates to unbroadcast test (Amiti Uttarwar)
dab298d9ab [docs] add release notes (Amiti Uttarwar)

Pull request description:

  This PR is a follow up to #18038 which introduced the idea of an unbroadcast set & focuses mostly on documentation updates and test fixes. One small functionality update to not throw an expected error in `LoadMempool` when you upgrade software versions.

  #18895 is another follow up to that addresses other functionality updates.

  Background context:
  The unbroadcast set is a mechanism for the mempool to track locally submitted transactions (via wallet or RPC). The node does a best-effort of delivering the transactions to the network via retries every 10-15 minutes until either a `GETDATA` is received or the transaction is removed from the mempool.

ACKs for top commit:
  MarcoFalke:
    ACK 9e1cb1adf1 👁
  gzhao408:
    ACK [`9e1cb1a`](9e1cb1adf1)

Tree-SHA512: 0cd51c4ca368b9dce92d50d73ec6e9df278a259e609eef2858f24cb8595ad07acc3db781d9eb0c351715f18fca5a2b4526838981fdb34a522427e9dc868bdaa6

doc/release-notes.md

@@ -65,9 +65,28 @@ Notable changes
 P2P and network changes
 -----------------------
 
+- The mempool now tracks whether transactions submitted via the wallet or RPCs
+  have been successfully broadcast. Every 10-15 minutes, the node will try to
+  announce unbroadcast transactions until a peer requests it via a `getdata`
+  message or the transaction is removed from the mempool for other reasons.
+  The node will not track the broadcast status of transactions submitted to the
+  node using P2P relay. This version reduces the initial broadcast guarantees
+  for wallet transactions submitted via P2P to a node running the wallet. (#18038)
+
 Updated RPCs
 ------------
 
+- `getmempoolinfo` now returns an additional `unbroadcastcount` field. The
+  mempool tracks locally submitted transactions until their initial broadcast
+  is acknowledged by a peer. This field returns the count of transactions
+  waiting for acknowledgement.
+
+- Mempool RPCs such as `getmempoolentry` and `getrawmempool` with
+  `verbose=true` now return an additional `unbroadcast` field. This indicates
+  whether initial broadcast of the transaction has been acknowledged by a
+  peer. `getmempoolancestors` and `getmempooldescendants` are also updated.
+
+
 Changes to Wallet or GUI related RPCs can be found in the GUI or Wallet section below.
 
 New RPCs
@@ -87,6 +106,13 @@ New settings
 Wallet
 ------
 
+- To improve wallet privacy, the frequency of wallet rebroadcast attempts is
+  reduced from approximately once every 15 minutes to once every 12-36 hours.
+  To maintain a similar level of guarantee for initial broadcast of wallet
+  transactions, the mempool tracks these transactions as a part of the newly
+  introduced unbroadcast set. See the "P2P and network changes" section for
+  more information on the unbroadcast set. (#18038)
+
 #### Wallet RPC changes
 
 - The `upgradewallet` RPC replaces the `-upgradewallet` command line option.