Respect framework partition set while merging meta files

The framework_partition_set would be generated from
framework_item_list and we should respect this partition
set while merging META/ab_partitions.txt.

This is to handle the case when we use a complete merged
target files package as the framework-target-files, where
its ab_partitions.txt may have non-framework partitions.
So we need to filter them out to prevent from the merged
meta file has some partitions that don't exist.

Test: merge_target_files &&
        add_img_to_target_files &&
	img_from_target_files &&
	flash device
Bug: 300193612
Change-Id: I0a76d706a20dcaffa2533278db7383563f03ec02