AppManager gives developers the ability to manage installed apllications.
PackageInstaller gives developers the ability to install, uninstall and
upgrade applications in unattended/silent mode.
PackageInstallerResult is the base element of the List passed by
onResult(List) to retrieve the result of
operations of install/uninstall/upgrade.
PackageInstallerSession gives developers the ability to group the execution of a sequence of install, uninstall and