freertos: Tidy up test organization

Some tests were placed in the incorrect test groups (i.e., kernel, port,
performance etc). This commit fixes those placements.

The following redundant tests were also removed:

- "test_panic.c" as behavior is already covered in esp_system tests

components/freertos/test_apps/freertos/misc/test_panic.c

@@ -1,25 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
-/*
- Test for multicore FreeRTOS. This test spins up threads, fiddles with queues etc.
-*/
-
-#include <esp_types.h>
-#include <stdio.h>
-
-#include "freertos/FreeRTOS.h"
-#include "freertos/task.h"
-#include "freertos/semphr.h"
-#include "freertos/queue.h"
-#include "unity.h"
-
-TEST_CASE("Panic handler", "[freertos][ignore]")
-{
-    volatile int *i;
-    i = (volatile int *)0x0;
-    *i = 1;
-}