scripted-diff: Replace MilliSleep with UninterruptibleSleep

This is safe because MilliSleep is never executed in a boost::thread,
the only type of thread that is interruptible.

* The RPC server uses std::thread
* The wallet is either executed in an RPC thread or the main thread
* bitcoin-cli, benchmarks and tests are only one thread (the main thread)

-BEGIN VERIFY SCRIPT-
sed -i --regexp-extended -e 's/MilliSleep\((\S+)\);/UninterruptibleSleep(std::chrono::milliseconds{\1});/g' $(git grep -l MilliSleep)
-END VERIFY SCRIPT-

src/httprpc.cpp

@@ -174,7 +174,7 @@ static bool HTTPReq_JSONRPC(HTTPRequest* req, const std::string &)
         /* Deter brute-forcing
            If this results in a DoS the user really
            shouldn't have their RPC port exposed. */
-        MilliSleep(250);
+        UninterruptibleSleep(std::chrono::milliseconds{250});
 
         req->WriteHeader("WWW-Authenticate", WWW_AUTH_HEADER_DATA);
         req->WriteReply(HTTP_UNAUTHORIZED);