refactor(spi_flash): reorganize header files and improve API encapsulation

This commit reorganizes SPI flash header files to better reflect their
visibility and intended usage:

1. Rename `esp_flash_port/` to `esp_flash_chips/`:
   - Better reflects that these headers are for chip driver implementations
   - All chip driver headers moved to `esp_flash_chips/` directory
   - Added README.md explaining semi-public nature of these headers

2. Move internal headers to `esp_private/`:
   - `esp_flash_internal.h` -> `esp_private/esp_flash_internal.h`
   - `memspi_host_driver.h` -> `esp_private/memspi_host_driver.h`

3. Move chip driver related headers to `esp_flash_chips/`:
   - `esp_private/esp_flash_types.h` -> `esp_flash_chips/esp_flash_types.h`
   - `spi_flash/spi_flash_defs.h` -> `esp_flash_chips/spi_flash_defs.h`
   - `spi_flash_override.h` -> `esp_flash_chips/spi_flash_override.h`
   - All `spi_flash_chip_*.h` headers moved to `esp_flash_chips/`

4. Code improvements:
   - Remove unused includes (e.g., `spi_flash_override.h` from `cache_utils.c`)
   - Use public API `esp_flash_get_size()` instead of direct member access
   - Add `esp_flash_is_quad_mode` to linker.lf for IRAM placement

5. Documentation updates:
   - Add README.md in `esp_flash_chips/` explaining semi-public headers
   - Update programming guide with warnings about internal headers
   - Update both English and Chinese documentation

6. Update all references across the codebase:
   - Update includes in `spi_flash` component
   - Update `bootloader_support`, `app_update`, `esp_tee`, `espcoredump`
   - Update example projects

Breaking changes:
- Headers moved to new locations require include path updates
- `custom_flash_driver` example temporarily disabled until external
  components are updated

components/spi_flash/esp_flash_spi_init.c

@@ -1,13 +1,10 @@
 /*
- * SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
 #include "sdkconfig.h"
-#include "esp_flash.h"
-#include "memspi_host_driver.h"
-#include "esp_flash_spi_init.h"
 #include "driver/gpio.h"
 #include "esp_rom_gpio.h"
 #include "esp_rom_efuse.h"
@@ -17,12 +14,8 @@
 #include "esp_private/spi_share_hw_ctrl.h"
 #include "esp_private/mspi_intr.h"
 #include "esp_ldo_regulator.h"
-#include "hal/spi_flash_hal.h"
-#include "esp_flash_port/spi_flash_chip_driver.h"
 #include "hal/gpio_hal.h"
-#include "esp_flash_internal.h"
 #include "esp_rom_gpio.h"
-#include "esp_private/spi_flash_os.h"
 #include "esp_private/cache_utils.h"
 #include "esp_private/log_util.h"
 #include "esp_private/startup_internal.h"
@@ -33,8 +26,16 @@
 #include "esp_private/esp_clk_tree_common.h"
 #include "clk_ctrl_os.h"
 #include "soc/soc_caps.h"
+#include "hal/spi_flash_hal.h"
 #include "hal/mspi_ll.h"
 
+#include "esp_flash.h"
+#include "esp_flash_spi_init.h"
+#include "esp_flash_chips/spi_flash_chip_driver.h"
+#include "esp_private/memspi_host_driver.h"
+#include "esp_private/esp_flash_internal.h"
+#include "esp_private/spi_flash_os.h"
+
 __attribute__((unused)) static const char TAG[] = "spi_flash";
 
 #if CONFIG_SPI_FLASH_ROM_IMPL && (CONFIG_ESPTOOLPY_FLASHSIZE_32MB || CONFIG_ESPTOOLPY_FLASHSIZE_64MB || CONFIG_ESPTOOLPY_FLASHSIZE_128MB)
@@ -357,12 +358,10 @@ static void deinit_gpspi_clock(esp_flash_t *chip)
     // Disable the clock source
     esp_clk_tree_enable_src(chip->clock_source, false);
 
-#if SOC_SPI_SUPPORT_CLK_RC_FAST
     // Disable RC_FAST clock if it was used
-    if (chip->clock_source == SPI_CLK_SRC_RC_FAST) {
+    if ((soc_module_clk_t)chip->clock_source == SOC_MOD_CLK_RC_FAST) {
         periph_rtc_dig_clk8m_disable();
     }
-#endif
 #endif // !CONFIG_IDF_TARGET_ESP32
 }
 
@@ -668,3 +667,8 @@ ESP_SYSTEM_INIT_FN(init_flash, CORE, BIT(0), 130)
     return ESP_OK;
 }
 #endif // !CONFIG_APP_BUILD_TYPE_PURE_RAM_APP
+
+void esp_flash_spi_init_include_func(void)
+{
+    // Linker hook function, exists to make the linker examine this file
+}