rust_test_suite: ensure crate names are valid (#1248)
rust_test_suite: ensure crate names are valid (#1248)

I noticed this while setting up rust_test_suite auto-generation at
work. Seems like a simple enough fix.

Co-authored-by: Augie Fackler <ea3626c096f885f01baa7a147917c28ffc55f123@google.com>
bazelbuild/rules_rust,bazelbuild/rules_rust,bazelbuild/rules_rust,bazelbuild/rules_rust,bazelbuild/rules_rust