Add API to skip application enable in install flow

This CL addes a new API to PackageInstaller.SessionParams that can be
used to skip the app enable step during the package install flow. This
can be used by installers to keep the app's existing enabled state
after a upgrade instead of setting it to enabled by default.

This also corrects the variable userId used in the enable step to
currentUserId that was preventing it from enabling the app when
installed for all users.

Bug: 244430570
Test: atest PackageManagerShellCommandTest#testAppUpdateSkipEnable
Change-Id: I42b003f8c42a7f8c45a581bd9383c78090462d0f