add testcases for rust output file paths

Prepare for changing rust rules by testing that output file names will
match. A build failure in b/301463284 was partially caused by output paths changing and resulting in old files building up on buildbots which filled the disk. This unit test will ensure that the file paths of rust modules do not change and cause the same failure.

Bug: 301463284
Bug: 286077158
Change-Id: I1baba2c63ad29a2c98e378fce0a2ed32bc319c1e