Add esp32s2 safe mode support & fix user_safe_mode output

[microdev1]

Please go through issue #3389 for a background of this PR.

What works:

• On esp32s2, one can manually enter safe mode by pressing boot button during the 700ms loop on startup. This loop is indicated by:
  • yellow color on rgb led and/or,
  • a blinking led
    Note: If you do not have any way of guessing the loop status, power-on the board/press the reset button and after a short delay, press and hold boot button for a while
• This PR also fixes the output of USER_SAFE_MODE which provides a board specific reason for entering safe mode.

To-do:

As of now when boot button is pressed esp32s2 doesn't perform a soft_reboot with safe_mode data stored in ram, instead it continues to boot with safe_mode status being USER_SAFE_MODE and finally ends up in safe mode. This workflow is not consistent with other CPY ports where a reset is performed and safe mode is entered on next boot.

To address this the following needs to be implemented:

1. Instead of returning USER_SAFE_MODE in function wait_for_safe_mode_reset(), soft_reboot needs to be called.
2. port_set_saved_word() function needs to edited in order to save safe_mode status in ram for the next boot.

[tannewt]

This looks great! This essentially does match behavior of other ports already and this doesn't need to change.

We will need the soft reboot approach for other safe mode failures though.

[microdev1]

Yes, for other safe mode failures soft reboot approach is needed.
Also, I get weird text formatting issues when using screen utility as my serial console.

[microdev1]

Current Status:

• soft reboot approach is not yet implemented,
  some core functions need to be updated before it can be properly implemented.

What changed:
(since last review)

• A fall-through reason was added in case BOARD_USER_SAFE_MODE_ACTION is not defined in the board specific config file.
• There was a text formatting issue which I traced back to serial_write("\n") , it advances a line but doesn't set the cursor to the beginning of the next line. Fixed.
  This issue was only evident in UNIX based serial console environment.

[jepler]

Thanks for working on this! I have some comments that probably stem from me suggesting incorrect code on Discord, I've tried to correct it and explain my logic.

[jepler]

Thanks for making the changes I requested!