Excessive warning statements printed out while running the regression

[adpaco]

A large blob of warning statements is being printed out while running the regression. Looks like it is happening in all testing scripts.

[adpaco]

The Rust team has changed the way they treat warnings so they are printed by default. See the discussion and the change.

We are keeping this issue open until we clean all warnings.

[zhassan-aws]

The warnings are specifically coming from these two:

1. scripts/codegen-firecracker.sh
2. src/test/rmc-multicrate/type-mismatch/run-mismatch-test.sh

[adpaco]

In my opinion, the long-term solution for this would be to figure out the type mismatch issue in #277. It points to an issue in the way we codegen slices. Other warnings (e.g., for concurrent features) are informative and it should be okay to have them printed during the regressions.

[adpaco]

Closing because the long-term solution was merged earlier this year in #1205. Thanks, @celinval ! 😄