chore: reduce some allocations collecting unstable features (#29827)

Minor thing.

cli/args/mod.rs

@@ -1030,19 +1030,20 @@ impl CliOptions {
       || self.workspace().has_unstable("sloppy-imports")
   }
 
-  pub fn unstable_features(&self) -> Vec<String> {
+  pub fn unstable_features(&self) -> Vec<&str> {
     let from_config_file = self.workspace().unstable_features();
     let unstable_features = from_config_file
       .iter()
+      .map(|s| s.as_str())
       .chain(
         self
           .flags
           .unstable_config
           .features
           .iter()
-          .filter(|f| !from_config_file.contains(f)),
+          .filter(|f| !from_config_file.contains(f))
+          .map(|s| s.as_str()),
       )
-      .map(|f| f.to_owned())
       .collect::<Vec<_>>();
 
     if !unstable_features.is_empty() {
@@ -1055,9 +1056,7 @@ impl CliOptions {
       // check and warn if the unstable flag of config file isn't supported, by
       // iterating through the vector holding the unstable flags
       for unstable_value_from_config_file in &unstable_features {
-        if !all_valid_unstable_flags
-          .contains(&unstable_value_from_config_file.as_str())
-        {
+        if !all_valid_unstable_flags.contains(unstable_value_from_config_file) {
           log::warn!(
             "{} '{}' isn't a valid unstable feature",
             colors::yellow("Warning"),

cli/factory.rs

@@ -944,7 +944,7 @@ impl CliFactory {
       checker.set_exit_cb(Box::new(crate::unstable_exit_cb));
       let unstable_features = cli_options.unstable_features();
       for feature in deno_runtime::UNSTABLE_FEATURES {
-        if unstable_features.contains(&feature.name.to_string()) {
+        if unstable_features.contains(&feature.name) {
           checker.enable_feature(feature.name);
         }
       }

cli/standalone/binary.rs

@@ -712,7 +712,12 @@ impl<'a> DenoCompileBinaryWriter<'a> {
         subdomain_wildcards: self.cli_options.unstable_subdomain_wildcards(),
         bare_node_builtins: self.cli_options.unstable_bare_node_builtins(),
         detect_cjs: self.cli_options.unstable_detect_cjs(),
-        features: self.cli_options.unstable_features(),
+        features: self
+          .cli_options
+          .unstable_features()
+          .into_iter()
+          .map(|s| s.to_string())
+          .collect(),
         lazy_dynamic_imports: self.cli_options.unstable_lazy_dynamic_imports(),
         npm_lazy_caching: self.cli_options.unstable_npm_lazy_caching(),
         sloppy_imports: self.cli_options.unstable_sloppy_imports(),