PYCBC-1675: Forward append/prepend CAS to core request

Motivation
==========
Previously the append and prepend requests in the C++ core did not have a field for CAS. This meant that the relevant option in AppendOptions/PrependOptions was being ignored.

Changes
=======
* Update C++ core & make some changes in response to API changes of the core's with_bucket_configuration() method.
* Set the CAS option in the core's append_request & prepend_request.

Results
=======
Relevant tests in FIT pass.

Change-Id: Iea541e43a6807500fdb54ce2335269a236a647f5
Reviewed-on: https://review.couchbase.org/c/couchbase-python-client/+/225076
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Jared Casey <jared.casey@couchbase.com>

Author: DemetrisChr

deps/couchbase-cxx-client

@@ -331,8 +331,7 @@ prepare_and_execute_binary_mutation_op(struct binary_mutation_options* options,
   if (options->op_type == Operations::APPEND) {
     auto req = couchbase::core::operations::append_request{ options->id };
     req.timeout = options->timeout_ms;
-    // @TODO:  cxx client req doesn't have cas
-    // req.cas = options->cas;
+    req.cas = options->cas;
     req.value = value;
     if (nullptr != options->span) {
       req.parent_span = std::make_shared<pycbc::request_span>(options->span);
@@ -355,8 +354,7 @@ prepare_and_execute_binary_mutation_op(struct binary_mutation_options* options,
   } else {
     auto req = couchbase::core::operations::prepend_request{ options->id };
     req.timeout = options->timeout_ms;
-    // @TODO:  cxx client req doesn't have cas
-    // req.cas = options->cas;
+    req.cas = options->cas;
     req.value = value;
     if (nullptr != options->span) {
       req.parent_span = std::make_shared<pycbc::request_span>(options->span);

src/binary_ops.cxx

@@ -198,19 +198,15 @@ handle_kv_range_scan_op([[maybe_unused]] PyObject* self, PyObject* args, PyObjec
     return nullptr;
   }
 
-  auto barrier = std::make_shared<
-    std::promise<tl::expected<couchbase::core::topology::configuration, std::error_code>>>();
+  auto barrier = std::make_shared<std::promise<
+    std::pair<std::error_code, std::shared_ptr<couchbase::core::topology::configuration>>>>();
   auto f = barrier->get_future();
-  conn->cluster_.with_bucket_configuration(
-    bucket_name,
-    [barrier](std::error_code ec, const couchbase::core::topology::configuration& config) mutable {
-      if (ec) {
-        return barrier->set_value(tl::unexpected(ec));
-      }
-      barrier->set_value(config);
-    });
-  auto config = f.get();
-  if (!config.has_value()) {
+  conn->cluster_.with_bucket_configuration(bucket_name,
+                                           [barrier](std::error_code ec, auto config) mutable {
+                                             barrier->set_value({ ec, std::move(config) });
+                                           });
+  auto [ec, config] = f.get();
+  if (ec) {
     pycbc_set_python_exception(
       PycbcError::UnsuccessfulOperation,
       __FILE__,