A new approach for erasing WiFi Settings (#8828)

* A new approach for erasing WiFi Settings

Add support for hardware reset function call - simulates EXT_RST via HWDT.

Add reset selection to `ESP.eraseConfig()` for calling hardware reset
after erasing the WiFi Settings.

Update ArduinoOTA to use `ESP.eraseConfig(true)`

Externalized `ArduinoOTA.eraseConfigAndReset()`

Add OTA examples to illustrate using erase config changes.

* style
fixed confused example

* improve wording

* Add new state to retry eraseConfigAndReset

* Removed unreachable error test from examples.

Removed continuous retry of "eraseConfig" and allow the script to
assign an error handling option for "eraseConfig" failure.

Update example to use error handling option.

* In eboot for function ets_wdt_enable() added missing arguments

* Update comments and example

* Wording

* Rebuilt eboot.elf with current tools from ./get.py

* Requested changes.

* cleanup comments

* Update hardware_reset

Avoid using "[[noreturn]]" - not accepted for a .c file function
Updated to use __attribute__((noreturn)) to handle both .cpp and .c
file functions.

bootloaders/eboot/eboot.c

@@ -17,8 +17,39 @@
 
 #define SWRST do { (*((volatile uint32_t*) 0x60000700)) |= 0x80000000; } while(0);
 
-extern void ets_wdt_enable(void);
-extern void ets_wdt_disable(void);
+/*
+  After Power Enable Pin, EXT_RST, or HWDT event, at "main()" in eboot, WDT is
+  disabled. Key WDT hardware registers are zero.
+
+  After "ESP.restart()" and other soft restarts, at "main()" in eboot, WDT is enabled.
+
+  References for the under-documented ets_wdt_* API
+    https://mongoose-os.com/blog/esp8266-watchdog-timer/
+    http://cholla.mmto.org/esp8266/bootrom/boot.txt
+
+  After looking at esp8266-watchdog-timer some more, `ets_wdt_enable(4, 12, 12)`
+  is good for eboot's needs. From a ".map" the NON-OS SDK does not use the
+  ets_wdt_* APIs, so our choices are not too critical.
+  The SDK will set up the WDT as it wants it.
+
+  A rationale for keeping the "ets_wdt_enable()" line, if the system is not
+  stable during a "soft restart," the HWDT would provide a recovery reboot.
+*/
+extern void ets_wdt_enable(uint32_t mode, uint32_t arg1, uint32_t arg2);
+/*
+  "ets_wdt_disable"
+
+  Diables WDT, then feeds the dog.
+  For current modes other than 1 or 2, returns the current mode.
+  For current mode 1, calls ets_timer_disarm, then return the current mode.
+  For current mode 2, calls ets_isr_mask, then return the current mode.
+
+  I always see a return value of 0xFFFFFFFF.
+
+  The return value would normally be used with ets_wdt_restore; however, that is
+  not an option since a valid prior call to ets_wdt_enable() may not have been done.
+*/
+extern uint32_t ets_wdt_disable(void);
 
 int print_version(const uint32_t flash_addr)
 {
@@ -241,12 +272,12 @@ int main()
 
         ets_wdt_disable();
         res = copy_raw(cmd.args[0], cmd.args[1], cmd.args[2], false);
-        ets_wdt_enable();
+        ets_wdt_enable(4, 12, 12);  // WDT about 13 secs.
 
         ets_printf("%d\n", res);
 #if 0
-	//devyte: this verify step below (cmp:) only works when the end of copy operation above does not overwrite the 
-	//beginning of the image in the empty area, see #7458. Disabling for now. 
+	//devyte: this verify step below (cmp:) only works when the end of copy operation above does not overwrite the
+	//beginning of the image in the empty area, see #7458. Disabling for now.
         //TODO: replace the below verify with hash type, crc, or similar.
         // Verify the copy
         ets_printf("cmp:");
@@ -257,7 +288,7 @@ int main()
             }
 
         ets_printf("%d\n", res);
-#endif	    
+#endif
         if (res == 0) {
             cmd.action = ACTION_LOAD_APP;
             cmd.args[0] = cmd.args[1];