feat(error): deprecate E_USER_ERROR in PHP 8.4

Refs: #476

Author: Xenira

src/embed/mod.rs

@@ -287,7 +287,7 @@ mod tests {
     #[test]
     fn test_eval_bailout() {
         Embed::run(|| {
-            let result = Embed::eval("trigger_error(\"Fatal error\", E_USER_ERROR);");
+            let result = Embed::eval("trigger_error(\"Fatal error\", E_ERROR);");
 
             assert!(result.is_err());
             assert!(result.unwrap_err().is_bailout());

src/flags.rs

@@ -308,6 +308,7 @@ bitflags! {
         /// Compile warning
         const CompileWarning = E_COMPILE_WARNING;
         /// User error
+        #[cfg_attr(php84, deprecated = "`E_USER_ERROR` is deprecated since PHP 8.4. Throw an exception instead.")]
         const UserError = E_USER_ERROR;
         /// User warning
         const UserWarning = E_USER_WARNING;