add back the exception to the error logging when loading an extension fails (#49075)

(cherry picked from commit d7df15d)

Author: KristofferC

base/loading.jl

@@ -1196,8 +1196,9 @@ function run_extension_callbacks(extid::ExtensionId)
         true
     catch
         # Try to continue loading if loading an extension errors
+        errs = current_exceptions()
         @error "Error during loading of extension $(extid.id.name) of $(extid.parentid.name), \
-                use `Base.retry_load_extensions()` to retry."
+                use `Base.retry_load_extensions()` to retry." exception=errs
         false
     end
     return succeeded