Bugfix for crash when scanning while attempting to join

[someone42]

The main commit here (1af351e) is to deal with an issue where if esp32-wifi-manager is attempting to join an AP using stored AP details and can't join, when it attempts to scan for new APs there will be a crash. For example:

• User successfully connects ESP32 to their home router AP
• User's home router AP spontaneously combusts
• esp32-wifi-manager can't connect to user's home router AP, after CONFIG_WIFI_MANAGER_MAX_RETRY_START_AP tries it brings up its own AP
• User purchases new router
• User connects to esp32-wifi-manager to switch it over to the new router

esp32-wifi-manager will then crash. This is because join attempts to the old router are still happening in the background, but the user connecting to esp32-wifi-manager's AP will trigger scan requests. As per esp-idf documentation (https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/wifi.html#scan-when-wi-fi-is-connecting), esp_wifi_scan_start() will fail immediately if a join attempt is in progress. The use of the ESP_ERROR_CHECK macro then causes a crash.

The commit introduces a software timer which will retry the scan later if it fails.

The other commit (9ddab86) is just something to deal with compilation errors I was getting when trying to include wifi_manger.h in my own application.

[dzanis]

someone42 thank you friend. This helped fix the incorrect password error. :) ESP32C3 Error if password incorrect