Clean up which/which-support Cargo feature (#5019)

* Rename "which" feature to "which-support"

* Ignore currently broken environment tests

crates/nu-command/src/core_commands/version.rs

@@ -256,7 +256,7 @@ fn features_enabled() -> Vec<String> {
         names.push("uuid".to_string());
     }
 
-    #[cfg(feature = "which")]
+    #[cfg(feature = "which-support")]
     {
         names.push("which".to_string());
     }

crates/nu-command/src/default_context.rs

@@ -142,7 +142,7 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
             Sys,
         };
 
-        #[cfg(feature = "which")]
+        #[cfg(feature = "which-support")]
         bind_command! { Which };
 
         // Strings

crates/nu-command/src/system/which_.rs

@@ -128,7 +128,7 @@ fn get_entries_in_nu(
     all_entries
 }
 
-#[cfg(feature = "which")]
+#[cfg(feature = "which-support")]
 fn get_first_entry_in_path(
     item: &str,
     span: Span,
@@ -140,7 +140,7 @@ fn get_first_entry_in_path(
         .ok()
 }
 
-#[cfg(not(feature = "which"))]
+#[cfg(not(feature = "which-support"))]
 fn get_first_entry_in_path(
     _item: &str,
     _span: Span,
@@ -150,7 +150,7 @@ fn get_first_entry_in_path(
     None
 }
 
-#[cfg(feature = "which")]
+#[cfg(feature = "which-support")]
 fn get_all_entries_in_path(
     item: &str,
     span: Span,
@@ -165,7 +165,7 @@ fn get_all_entries_in_path(
         .unwrap_or_default()
 }
 
-#[cfg(not(feature = "which"))]
+#[cfg(not(feature = "which-support"))]
 fn get_all_entries_in_path(
     _item: &str,
     _span: Span,