fdo#54938 Convert extensions to cppu::supportsService

Change-Id: If3675c28a204168d7385b1421dbb70b2a9b719e2
Reviewed-on: https://gerrit.libreoffice.org/7648
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Marcos Souza <marcos.souza.org@gmail.com>
Tested-by: Marcos Souza <marcos.souza.org@gmail.com>