all: don't automatically convert userdata types to pointer types

One of the things I have not learned but done a better job of
internalizing while working with zig over the last few months is that
the less magic that exists, the better. In the case of parameterized
functions, this means that it is much better to restrict the range of
types that are permitted to be passed than to perform type
manipulation. In other words, it's more confusing to see a function
that is parameterized with `SomeType` taking a pointer to that type
than having it be parameterized directly to take the pointer.
Obviously there are exceptions to this rule, like std.mem.eql taking
slices of its parameterized type.

tests/connection.zig

@@ -164,14 +164,14 @@ test "nats.ConnectionOptions" {
     try options.setMaxReconnect(10);
     try options.setReconnectWait(500);
     try options.setReconnectJitter(100, 200);
-    try options.setCustomReconnectDelay(u32, reconnectDelayHandler, &userdata);
+    try options.setCustomReconnectDelay(*u32, reconnectDelayHandler, &userdata);
     try options.setReconnectBufSize(1024);
     try options.setMaxPendingMessages(50);
-    try options.setErrorHandler(u32, errorHandler, &userdata);
-    try options.setClosedCallback(u32, connectionHandler, &userdata);
-    try options.setDisconnectedCallback(u32, connectionHandler, &userdata);
-    try options.setDiscoveredServersCallback(u32, connectionHandler, &userdata);
-    try options.setLameDuckModeCallback(u32, connectionHandler, &userdata);
+    try options.setErrorHandler(*u32, errorHandler, &userdata);
+    try options.setClosedCallback(*u32, connectionHandler, &userdata);
+    try options.setDisconnectedCallback(*u32, connectionHandler, &userdata);
+    try options.setDiscoveredServersCallback(*u32, connectionHandler, &userdata);
+    try options.setLameDuckModeCallback(*u32, connectionHandler, &userdata);
     try options.ignoreDiscoveredServers(true);
     try options.useGlobalMessageDelivery(false);
     try options.ipResolutionOrder(.ipv4_first);
@@ -179,8 +179,8 @@ test "nats.ConnectionOptions" {
     try options.useOldRequestStyle(false);
     try options.setFailRequestsOnDisconnect(true);
     try options.setNoEcho(true);
-    try options.setRetryOnFailedConnect(u32, connectionHandler, true, &userdata);
-    try options.setUserCredentialsCallbacks(u32, u32, jwtHandler, signatureHandler, &userdata, &userdata);
+    try options.setRetryOnFailedConnect(*u32, connectionHandler, true, &userdata);
+    try options.setUserCredentialsCallbacks(*u32, *u32, jwtHandler, signatureHandler, &userdata, &userdata);
     try options.setWriteDeadline(5);
     try options.disableNoResponders(true);
     try options.setCustomInboxPrefix("_FOOBOX");
@@ -200,7 +200,7 @@ test "nats.ConnectionOptions (crypto edition)" {
     defer options.destroy();
     var userdata: u32 = 0;
 
-    try options.setTokenHandler(u32, tokenHandler, &userdata);
+    try options.setTokenHandler(*u32, tokenHandler, &userdata);
     try options.setSecure(false);
     try options.setCertificatesChain(rsa_cert, rsa_key);
     try options.setCiphers("-ALL:HIGH");

tests/subscription.zig

@@ -113,7 +113,7 @@ test "nats.Subscription (async)" {
 
     {
         var count: u32 = 0;
-        const subscription = try connection.subscribe(u32, message_subject, onMessage, &count);
+        const subscription = try connection.subscribe(*u32, message_subject, onMessage, &count);
         defer subscription.destroy();
 
         const response = try connection.requestMessage(message, 1000);
@@ -126,7 +126,7 @@ test "nats.Subscription (async)" {
     {
         var count: u32 = 0;
         const subscription = try connection.subscribeTimeout(
-            u32,
+            *u32,
             message_subject,
             1000,
             onMessage,
@@ -144,7 +144,7 @@ test "nats.Subscription (async)" {
     {
         var count: u32 = 0;
         const subscription = try connection.queueSubscribe(
-            u32,
+            *u32,
             message_subject,
             "queuegroup",
             onMessage,
@@ -162,7 +162,7 @@ test "nats.Subscription (async)" {
     {
         var count: u32 = 0;
         const subscription = try connection.queueSubscribeTimeout(
-            u32,
+            *u32,
             message_subject,
             "queuegroup",
             1000,