Dist art module's public api in 'art.txt'

This also has the side-effect of enabling tracking compatibility of
the API with the api released in SDK version 30 (via txt files added in
prebuilt/sdk in this topic).

Bug: 174847574
Test: m dist sdk (inspect out/dist/apistubs)
Change-Id: I6d2c936d38ec6e5bd3d4a2a7e61a7deda7bcd210
1 file changed