Secretkeeper: move VTS to rdroidtest

Use rdroidtest for running tests as it now supports parameterized
tests (aosp/2885268) and has an attribute macro (aosp/2890086).

Also rustfmt.

Test: VtsSecretkeeperTargetTest
Change-Id: I9570a7f33a6ff7dbf7cb7238fa3770dedb990e8c