liblp: Remove alignment_offset handling.

This code is complex and alignment_offset is not useful for
optimization. Remove it, and add another test that misaligned extents do
not cause overlapping partitions.

Bug: 154646936
Test: liblp_test gtests
Change-Id: I563122282e940e07a7ece97ed1a9846ad1f3253c
5 files changed