CI: Add fuzz to CRATES

The `fuzz` crate should be included in the `CRATES` variable. In
`run_task` it is only built (not tested) using `cargo --locked build`.

When the `fuzz` crate is used in the `bench` job all the dead code
combined with the `deny` attribute causes the `bench` job to fail.

Because we have a lint job we can soften the restriction to warnings wit
no loss of cover.

Author: tcharding

contrib/crates.sh

@@ -4,5 +4,5 @@
 # disable verify unused vars, despite the fact that they are used when sourced
 # shellcheck disable=SC2034
 
-# Crates in this workspace to test (excl. fuzz an integration-tests).
-CRATES=(".")                    # Non-workspaces don't have crates.
+# Crates in this workspace to test.
+CRATES=("." "fuzz")

src/lib.rs

@@ -82,7 +82,7 @@
 #![deny(non_camel_case_types)]
 #![deny(non_snake_case)]
 #![deny(unused_mut)]
-#![deny(dead_code)]
+#![warn(dead_code)]
 #![deny(unused_imports)]
 #![deny(missing_docs)]
 // Clippy lints that we have disabled