Fix a few issues in Client

Most significantly, if removing from the multi fails, the connection
is added to a "dirty" list for the removal to be retried later. Looking at
the curl source code, remove fails on a recursive call, and we've struggled with
recursive calls before, so I _think_ this might be happening (it fails in other
cases, but I suspect if it _is_ happening, it's for this reason). The retry
happens _after_ `perform`, so it cannot fail for due to recursiveness. If it
fails at this point, we @panic. This is harsh, but it isn't easily recoverable
and before putting effort into it, I'd like to know that it's actually happening.

Fix potential use of undefined when a 401-407 request is received, but no
'WWW-Authenticate' or 'Proxy-Authenticate' header is received.

Don't call `curl_multi_remove_handle` on an easy that hasn't been added yet do
to error. Specifically, if `makeRequest` fails during setup, transfer_conn is
nulled so that `transfer.deinit()` doesn't try to remove the connection. And the
conn is removed from the `in_use` queue and made `available` again.

On Abort, if getting the private fails (extremely unlikely), we now still try
to remove the connection from the multi.

Added a few more fields to the famous "ScriptManager.Header recall" assertion.

src/cdp/domains/fetch.zig

@@ -406,10 +406,10 @@ pub fn requestAuthRequired(bc: anytype, intercept: *const Notification.RequestAu
             .fetch => "Fetch",
         },
         .authChallenge = .{
-            .source = if (challenge.source == .server) "Server" else "Proxy",
             .origin = "", // TODO get origin, could be the proxy address for example.
-            .scheme = if (challenge.scheme == .digest) "digest" else "basic",
-            .realm = challenge.realm,
+            .source = if (challenge.source) |s| (if (s == .server) "Server" else "Proxy") else "",
+            .scheme = if (challenge.scheme) |s| (if (s == .digest) "digest" else "basic") else "",
+            .realm = challenge.realm orelse "",
         },
         .networkId = &id.toRequestId(transfer.id),
     }, .{ .session_id = session_id });