The qtwebengine needs to pass information about where the
QtWebEngineProcess is located for Conan as each Qt package is installed
under separate install prefix inside the Conan cache.

Locate the QtWebEngineProcess from the installation folder under the
qtwebengine install prefix inside the Conan cache.
Return a dictionary where 'QTWEBENGINEPROCESS_PATH' points to the
located QtWebEngineProcess file.

Pick-to: 6.2 6.3 6.3.2 6.4
Change-Id: I54da22eae3b0e7cca0b1a19e683f661ccf21d219
Reviewed-by: Toni Saario <toni.saario@qt.io>