Userland: Rename IPC ClientConnection => ConnectionFromClient

This was done with CLion's automatic rename feature and with:
find . -name ClientConnection.h
    | rename 's/ClientConnection\.h/ConnectionFromClient.h/'

find . -name ClientConnection.cpp
    | rename 's/ClientConnection\.cpp/ConnectionFromClient.cpp/'

Userland/Libraries/LibIPC/ConnectionFromClient.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibIPC/Connection.h>
+
+namespace IPC {
+
+template<typename T, class... Args>
+NonnullRefPtr<T> new_client_connection(Args&&... args)
+{
+    return T::construct(forward<Args>(args)...) /* arghs */;
+}
+
+template<typename ClientEndpoint, typename ServerEndpoint>
+class ConnectionFromClient : public Connection<ServerEndpoint, ClientEndpoint>
+    , public ServerEndpoint::Stub
+    , public ClientEndpoint::template Proxy<ServerEndpoint> {
+public:
+    using ServerStub = typename ServerEndpoint::Stub;
+    using IPCProxy = typename ClientEndpoint::template Proxy<ServerEndpoint>;
+
+    ConnectionFromClient(ServerStub& stub, NonnullOwnPtr<Core::Stream::LocalSocket> socket, int client_id)
+        : IPC::Connection<ServerEndpoint, ClientEndpoint>(stub, move(socket))
+        , ClientEndpoint::template Proxy<ServerEndpoint>(*this, {})
+        , m_client_id(client_id)
+    {
+        VERIFY(this->socket().is_open());
+        this->socket().on_ready_to_read = [this] {
+            // FIXME: Do something about errors.
+            (void)this->drain_messages_from_peer();
+        };
+    }
+
+    virtual ~ConnectionFromClient() override
+    {
+    }
+
+    void did_misbehave()
+    {
+        dbgln("{} (id={}) misbehaved, disconnecting.", *this, m_client_id);
+        this->shutdown();
+    }
+
+    void did_misbehave(const char* message)
+    {
+        dbgln("{} (id={}) misbehaved ({}), disconnecting.", *this, m_client_id, message);
+        this->shutdown();
+    }
+
+    void shutdown_with_error(Error const& error)
+    {
+        dbgln("{} (id={}) had error ({}), disconnecting.", *this, m_client_id, error);
+        this->shutdown();
+    }
+
+    int client_id() const { return m_client_id; }
+
+    virtual void die() override = 0;
+
+private:
+    int m_client_id { -1 };
+};
+
+}
+
+template<typename ClientEndpoint, typename ServerEndpoint>
+struct AK::Formatter<IPC::ConnectionFromClient<ClientEndpoint, ServerEndpoint>> : Formatter<Core::Object> {
+};