watchdog: make behavior across ports consistent

[jepler]

[based in part on discussion In The Weeds on the weekly meeting March 13, 2023]

• Make the behavior of watchdog at the end of code.py consistent:
  probably, only inactivate the watchdog in the case of KeyboardInterrupt or ReloadException.
• In shared-bindings permit assigning watchdog.mode = WatchDogMode.NONE if the underlying hardware supports it.
• Mark watchdog.deinit() as deprecated now.
• In a later version, remove the watchdog.deinit() method.

[jepler]

@microdev1 moving the discussion of how to make the watchdog consistent & how to handle resetting at interpreter exit here so that it does not block #7718 from being merged.

[vladak]

What's the story behind the removal of deinit() ? In my case, I call it before the device (Feather V2) is put to deep sleep, which happens periodically. Maybe calling it is not necessary in such case ?

[microdev1]

What's the story behind the removal of deinit() ?

The deinit functionality is still present, the API has changed. Instead of calling deinit(), set the watchdog mode to None.