Enable compat checking & lint for module_lib api

These were previously turned off as there were no previous
releases to compare it to. Check in empty files as comparison.

The new tethering APIs fail lint -- I have filed a release
blocking bug to get these cleaned up.

Bug: 149430003
Bug: 147559833
Test: m module-lib-api-api-lint
Test: m module-lib-api-check-last-released-api (with+without incompatibilities)
Change-Id: I2b171dc836ca121502fb345d8dd512a05c566a49
Merged-In: I2b171dc836ca121502fb345d8dd512a05c566a49
(cherry picked from commit 79e35c3b)