liblp: Fix tests for linear extent overlap.

The "OwnsSector" tests did not work if one range fit completely inside
another range. The new OverlapsWith() methods address this case.

Bug: 154277287
Bug: 154646936
Test: liblp_test gtests
Change-Id: I1a59069db4ffe4f13c45963c4847cff7b3dd3dfc