Move default app related methods to role manager.

Default apps (browser, dialer and home) are by no means a concept of
permission, so they should not be exposed as permission
manager API. Instead, they should be accessed via role manager API.

This change moves getDefaultBrowser() and setDefaultBrowser()'s AIDL
interface and implementation into RoleManagerService. Package manager
has a number of special behaviors regarding these default apps, so we
can not pretend that package manager doesn't know about these
roles. After all, we can say permission and role are at the same level
in the system after recent refactoring that split permission and
package. So package manager is reusing the public role API now.

The new methods moved to RoleManagerService needs to be system APIs on
RoleManager, because IRoleManager cannot be a system API and we need
to delegate method calls to it from ApplicationPackageManager.

The other methods directly calling into DefaultPermissionGrantPolicy
should be moved/refactored as well, depending on whether we want to
mainline it, in a later change.

Bug: 158736025
Test: presubmit
Change-Id: I84b9519a084e410875a3c3e88b33e9a612e7de98