Skip checking vendor partition size on AOSP targets

AOSP targets doesn't have INSTALLED_VENDORIMAGE_TARGET defined.

Fix dump-dynamic-partitions-info to filter out vendor
from dynamic partition lists.

Then, check_partition_sizes.py reads info without vendor
in dynamic partition list for AOSP targets.

Test: forrest
Bug: 143734706

Change-Id: I788196d854c1cf3eea218d534599f8bf642120fc