Resolve default alarm ringtone URI when computing their title

Default URI that resolves to an internal URI should always be allowed.
e.g. "Default (Oxygen)"

Default URI that resolves to an external URI should only be allowed
if the user has granted the READ_EXTERNAL_STORAGE permission.
e.g. "Custom Ringtone" without perm; "Default (Some Name)" with perm

Bug: 22855800
Change-Id: Ibca0f2dd99bcf297a46d309b16665023cc4bc725