Rename `EarlyDiagCtxt` methods to match `DiagCtxt`.

- `early_error_no_abort` -> `early_err`
- `early_error` -> `early_fatal`
- `early_struct_error` -> `early_struct_fatal`

src/base.rs

@@ -179,7 +179,7 @@ pub(crate) fn compile_fn(
                 let early_dcx = rustc_session::EarlyDiagCtxt::new(
                     rustc_session::config::ErrorOutputType::default(),
                 );
-                early_dcx.early_error(format!(
+                early_dcx.early_fatal(format!(
                     "backend implementation limit exceeded while compiling {name}",
                     name = codegened_func.symbol_name
                 ));