The clangdclient.cpp file is rather large, and the AST stuff is a nicely
self-contained chunk of code to move out.
No functional changes.
Change-Id: I0240413f561f5c67ca5ee310b5c4253ffa62fdae
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>
