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/Services/Clipboard/ConnectionFromClient.cpp

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Clipboard/ClipboardClientEndpoint.h>
+#include <Clipboard/ConnectionFromClient.h>
+#include <Clipboard/Storage.h>
+
+namespace Clipboard {
+
+static HashMap<int, RefPtr<ConnectionFromClient>> s_connections;
+
+void ConnectionFromClient::for_each_client(Function<void(ConnectionFromClient&)> callback)
+{
+    for (auto& it : s_connections) {
+        callback(*it.value);
+    }
+}
+
+ConnectionFromClient::ConnectionFromClient(NonnullOwnPtr<Core::Stream::LocalSocket> socket, int client_id)
+    : IPC::ConnectionFromClient<ClipboardClientEndpoint, ClipboardServerEndpoint>(*this, move(socket), client_id)
+{
+    s_connections.set(client_id, *this);
+}
+
+ConnectionFromClient::~ConnectionFromClient()
+{
+}
+
+void ConnectionFromClient::die()
+{
+    s_connections.remove(client_id());
+}
+
+void ConnectionFromClient::set_clipboard_data(Core::AnonymousBuffer const& data, String const& mime_type, IPC::Dictionary const& metadata)
+{
+    Storage::the().set_data(data, mime_type, metadata.entries());
+}
+
+Messages::ClipboardServer::GetClipboardDataResponse ConnectionFromClient::get_clipboard_data()
+{
+    auto& storage = Storage::the();
+    return { storage.buffer(), storage.mime_type(), storage.metadata() };
+}
+
+void ConnectionFromClient::notify_about_clipboard_change()
+{
+    async_clipboard_data_changed(Storage::the().mime_type());
+}
+
+}