Add a keep.xml to avoid aliases being stripped.
Add a keep.xml to avoid aliases being stripped.

In some situations the root aliases are being stripped, add a keep.xml
to hint to the shrinker to keep them.

Bug: 258478735
Test: Built and tried in breaking app
Change-Id: I66cbdbb9ea07b812267025354d3047e842f1bfa8

androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx