[Security Solution][Event Filters] Fix autocomplete infinite loop bug when deleting the field combobox in event filters form (#189980)

## Summary
- [x] Fixes a bug where the user would not be able to clear out the
Field combo box in the Event Filters form
- [x] Adds a clear out button to the field combo box

Testing steps:
- Navigate to Security > Manage > Event Filters > Add event filter
- Fill out the Field and Value section and select out of the builder
- Try to clear out field either by backspacing the selection or with the
`x` button
- Successfully clear out the field 

# Screenshots

![infinitebug](https://github.com/user-attachments/assets/05c40764-ea93-4650-8273-7212d78889c2)

---------

Co-authored-by: Tomasz Ciecierski <tomasz.ciecierski@elastic.co>
Co-authored-by: Ashokaditya <ashokaditya@elastic.co>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugins/lists/public/exceptions/components/builder/entry_renderer.tsx

@@ -220,7 +220,7 @@ export const BuilderEntryItem: React.FC<EntryItemProps> = ({
             exceptionItemIndex,
             entry.entryIndex
           )}
-          isClearable={false}
+          isClearable={true}
           isLoading={false}
           isDisabled={isDisabled || indexPattern == null}
           onChange={handleFieldChange}

x-pack/plugins/security_solution/public/management/pages/event_filters/view/components/form.tsx

@@ -575,7 +575,10 @@ export const EventFiltersForm: React.FC<ArtifactFormComponentProps & { allowSele
                 tags: exception?.tags ?? [],
                 meta: exception.meta,
               }
-            : exception;
+            : {
+                ...exception,
+                entries: [{ field: '', operator: 'included', type: 'match', value: '' }],
+              };
         const hasValidConditions =
           arg.exceptionItems[0] !== undefined
             ? !(arg.errorExists && !arg.exceptionItems[0]?.entries?.length)