Use the vcpkg manifest to configure and build QtGRPC chat example.
This allows automating the dependency installation using vcpkg.
Pick-to: 6.9
Task-number: QTBUG-132738
Change-Id: Iafcb8e144d51f1af0d775869550f003c997d106a
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>