[opt](load) catch Throwable to make load error msg more clear (apache…

…#26821)

When doing LoadPendingTask or LoadLoadingTask, there may be some Error thrown,
such as `NoClassDefFoundError`, but previously, we only catch java's `Exception`, so
other kind of error can not be shown clearly.

fe/fe-core/src/main/java/org/apache/doris/load/loadv2/LoadTask.java

@@ -91,10 +91,10 @@ protected void exec() {
             failMsg.setMsg(e.getMessage() == null ? "" : e.getMessage());
             LOG.warn(new LogBuilder(LogKey.LOAD_JOB, callback.getCallbackId())
                     .add("error_msg", "Failed to execute load task").build(), e);
-        } catch (Exception e) {
-            failMsg.setMsg(e.getMessage() == null ? "" : e.getMessage());
+        } catch (Throwable t) {
+            failMsg.setMsg(t.getMessage() == null ? "" : t.getMessage());
             LOG.warn(new LogBuilder(LogKey.LOAD_JOB, callback.getCallbackId())
-                    .add("error_msg", "Unexpected failed to execute load task").build(), e);
+                    .add("error_msg", "Unexpected failed to execute load task").build(), t);
         } finally {
             if (!isFinished) {
                 // callback on pending task failed