wallet: allowing walletpassphrase timeout to be set to MAX_SLEEP_TIME

In this change we allow the timeout for walletpassphrase to be
set to MAX_SLEEP_TIME,
if set as 0 then we then use the MAX_SLEEP_TIME amount

context from PR 28403

src/wallet/rpc/encrypt.cpp

@@ -18,7 +18,7 @@ RPCHelpMan walletpassphrase()
             "time that overrides the old one.\n",
                 {
                     {"passphrase", RPCArg::Type::STR, RPCArg::Optional::NO, "The wallet passphrase"},
-                    {"timeout", RPCArg::Type::NUM, RPCArg::Optional::NO, "The time to keep the decryption key in seconds; capped at 100000000 (~3 years)."},
+                    {"timeout", RPCArg::Type::NUM, RPCArg::Optional::NO, "The time to keep the decryption key in seconds; capped at 100000000 (~3 years), will use cap if 0 specified"},
                 },
                 RPCResult{RPCResult::Type::NONE, "", ""},
                 RPCExamples{
@@ -59,7 +59,7 @@ RPCHelpMan walletpassphrase()
         }
         // Clamp timeout
         constexpr int64_t MAX_SLEEP_TIME = 100000000; // larger values trigger a macos/libevent bug?
-        if (nSleepTime > MAX_SLEEP_TIME) {
+        if (nSleepTime > MAX_SLEEP_TIME || nSleepTime == 0) {
             nSleepTime = MAX_SLEEP_TIME;
         }