AOSP: e2fsdroid: Allow re-use of deduplicated blocks.

AOSP: e2fsdroid: Allow re-use of deduplicated blocks.

When using a Base FS map, track deduplicated blocks in a separate
bitmap. The first inode to request a block from this set will succeed
in getting the block. Blocks in the dedup set are not available for
libext2fs to allocate; this ensures that previously deduplicated blocks
are re-used for their original purpose.

Note that deduplication takes priority over block allocation, so that
once a block is removed from the dedup set, that does not actually
prevent it from being re-used. Similarly, a file that was not previously
sharing a block may have its blocks shared in the new image.

Bug: 145316683
Test: e2fsdroid with dynamic partitions
Change-Id: I73856faa5d294a7b5fb985ccd1a6974a989481ea
From AOSP commit: 4e55425ff5d7d7cea27dcf79125766762e2b3529