Fix inconsistent strum dependencies and imports (#40907)

The `scripts_traits` crate was the only crate depending on `strum` with
the
`derive` feature. This accidentally allowed other crates to import strum
macros via `strum::` without declaring their own dependency on
`strum_macros`,
causing compilation issues when running `./mach test-unit -p net`.

This PR makes the imports consistent across the code base by:
- replacing all `strum_macro::` imports with `strum::` imports
- removing strum_macro dependencies
- adding derive feature to the strum workspace

Testing: Unit tests continue to pass

Signed-off-by: Jan Varga <jvarga@igalia.com>

components/script/dom/processingoptions.rs

@@ -21,7 +21,7 @@ use net_traits::{FetchMetadata, NetworkError, ReferrerPolicy, ResourceFetchTimin
 pub use nom_rfc8288::complete::LinkDataOwned as LinkHeader;
 use nom_rfc8288::complete::link_lenient as parse_link_header;
 use servo_url::{ImmutableOrigin, ServoUrl};
-use strum_macros::IntoStaticStr;
+use strum::IntoStaticStr;
 
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::refcounted::Trusted;