LanguageClient: Add the possibility to override progress messages

... and make use of it in the clangd client.
We want the progress bar for background indexing to have a better title
than the plain (and non-translated) "indexing" that the clangd server
sends.

Change-Id: Ib75eac370e7c22f0c5bd477f4a4c423283b27e1f
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/languageclient/client.cpp

@@ -1019,6 +1019,12 @@ void Client::setError(const QString &message)
     m_state = Error;
 }
 
+void Client::setProgressTitleForToken(const LanguageServerProtocol::ProgressToken &token,
+                                      const QString &message)
+{
+    m_progressManager.setTitleForToken(token, message);
+}
+
 void Client::handleMessage(const BaseMessage &message)
 {
     LanguageClientManager::logBaseMessage(LspLogMessage::ServerMessage, name(), message);