Add a switch for pre-approval request

In case we decide not to provide pre-approval request to installer
for some reason (e.g., feature off), we need a way to disable this,
and let callers know the typical flow will be needed instead.

Bug: 242677131
Test: atest CtsPackageInstallTestCases:PreapprovalInstallTest
Change-Id: I42dead8044597238588dcf55ddd7d617ac21f671