Preventing a shortcut which requires permissions from being added to

homescreen

A shortcut can be added by any app as INSTALL_SHORTCUT is a normal
level permission. But the intent is actually launched by the launcher
app which can have other permission as well.

> When adding a shortcut from the broadcast, verify that the intent does
not require any permission
> When adding a shortcut using the two-step drop process, verify that
the source app also has the permission to create such a shortcut

Bug: 30778130
Change-Id: I710a490d69019dc25709db5a97020c20d9325007