refactor(mwdt): move sleep retention config into system layer

Move MWDT retention descriptors out of esp_hal_wdt and into esp_system
so the backup policy lives with the watchdog users, while keeping the
per-chip retention sources under the existing port/soc target
directories.

components/esp_hal_wdt/include/hal/mwdt_periph.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2019-2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2019-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -9,10 +9,6 @@
 #include <stdint.h>
 #include "soc/timer_group_reg.h"
 #include "soc/timer_group_struct.h"
-#include "soc/soc_caps.h"
-#include "soc/periph_defs.h"
-#include "soc/regdma.h"
-#include "hal/mwdt_ll.h"
 
 /* The value that needs to be written to TIMG_WDT_WKEY to write-enable the wdt registers */
 #define TIMG_WDT_WKEY_VALUE 0x50D83AA1
@@ -21,15 +17,6 @@
 extern "C" {
 #endif
 
-#if SOC_MWDT_SUPPORT_SLEEP_RETENTION && SOC_PAU_SUPPORTED
-typedef struct {
-    const regdma_entries_config_t *link_list;
-    uint32_t link_num;
-} tg_reg_ctx_link_t;
-
-extern const tg_reg_ctx_link_t tg_wdt_regs_retention[TIMG_LL_GET(INST_NUM)];
-#endif // SOC_MWDT_SUPPORT_SLEEP_RETENTION
-
 #ifdef __cplusplus
 }
 #endif