Merge bitcoin/bitcoin#34224: init: Return EXIT_SUCCESS on interrupt

997e7b4d7c init: Fix non-zero code on interrupt (sedited)

Pull request description:

  Reported by dergoegge on irc.

  An interrupt does not create a failure exit code during normal operation. This should also be the case when interrupt is triggered during initialization. However a failure exit code is currently returned if an interrupt occurs during init. Fix this by making `AppInitMain` return true instead of false on interrupt, which further up the call stack currently sets the `EXIT_FAILURE` code. Also add a check for the interrupt condition during GUI startup. Returning `EXIT_SUCCESS` seems to be the usual behaviour for daemons, see the discussion on IRC for this: https://www.erisian.com.au/bitcoin-core-dev/log-2026-01-08.html#l-146 .

  Best reviewed with `--color-moved=dimmed-zebra --color-moved-ws=ignore-all-space`.

ACKs for top commit:
  maflcko:
    review ACK 997e7b4d7c 🔺
  janb84:
    ACK 997e7b4d7c
  dergoegge:
    utACK 997e7b4d7c

Tree-SHA512: c9542e95d9312567e029426a329144b5bc638d8ebc9c966e0246c1bb728d40f56ca425b00c446f5d238067e629c2337d0fe78bcc5a8760424d2ec38a5578e115

src/init.cpp

@@ -1842,7 +1842,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     // requested to kill the GUI during the last operation. If so, exit.
     if (ShutdownRequested(node)) {
         LogInfo("Shutdown requested. Exiting.");
-        return false;
+        return true;
     }
 
     ChainstateManager& chainman = *Assert(node.chainman);
@@ -2018,7 +2018,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     }
 
     if (ShutdownRequested(node)) {
-        return false;
+        return true;
     }
 
     // ********************************************************* Step 12: start node