Run checkvintf with all staged apexes mounted

For a staged/multi-package installation, checkvintf should run with all
staged apexes mounted. Otherwise, it can't detect conflicts in two new
apexes.

Besides, checkvintf covers apexes with etc/vintf now because system-side
apexes can have VINTF manifests.

Bug: 364999002
Test: atest VendorApexHostTestCases
Change-Id: I8ed6c59aa57dc35cd02b11e5da2c72534afc15a9
10 files changed