mac_addr(C6 and H2): Fix byte order of MAC_EXT and change format of IEEE802154 MAC

The changes only related to C6 and H2 chips where CONFIG_SOC_IEEE802154_SUPPORTED=y.
For this case these APIs return 8 bytes
    esp_efuse_mac_get_default() -> 8 bytes
    esp_efuse_mac_get_custom() -> 8 bytes
    esp_read_mac(..., ESP_MAC_IEEE802154) -> 8 bytes
The rest cases len is 6 bytes

examples/system/.build-test-rules.yml

@@ -6,12 +6,6 @@ examples/system/app_trace_basic:
       temporary: true
       reason: target esp32c6, esp32h2 is not supported yet
 
-examples/system/base_mac_address:
-  disable_test:
-    - if: IDF_TARGET in ["esp32h2"]
-      temporary: true
-      reason: cannot pass, IDF-6809
-
 examples/system/console/advanced:
   disable_test:
     - if: IDF_TARGET not in ["esp32", "esp32c3"]