Move them from the bottom of src/proto.rs to its own src/tests/mod.rs.
Also drop the test_ prefix, this is not golang.
Change-Id: I2e0b6b9812264f3d9721c0766936f08157fadc66
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7667
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
