Allow configuration of wifi credentials + hostname via settings.json

What it says on the tin.

• Replaces the hardcoded camp wifi credentials with ssid + psk read from settings.json. Also allows configuration of the badge network hostname.
• Adds barebones code for string type 'tunables'/settings. (Read only, can only be set via settings.json at the moment)
• Declaratively define hierarchical settings (sub-)menu structure
  • Only WiFi settings have their own submenu for now

Known issues: Display of string settings values in the settings screen is a bit glitchy. Not quite sure why, but I also haven't spent much time debugging it since this is just a barebones implementation for the functionality and the display issue is purely cosmetic and doesn't affect the core features of this patch.

python_payload/st3m/goose.py

@@ -17,7 +17,7 @@ if TYPE_CHECKING:
     class ABCBase(metaclass=ABCMeta):
         pass
 
-    from typing import List, Optional, Tuple, Dict, Any, Callable, Iterator, Generator
+    from typing import List, Optional, Tuple, Dict, Any, Callable, Iterator, Generator, Union
     from enum import Enum
 else:
     # We're in CPython or Micropython.
@@ -40,6 +40,7 @@ else:
             Callable,
             Iterator,
             Generator,
+            Union,
         )
         from enum import Enum
     except ImportError:
@@ -52,6 +53,7 @@ else:
         Callable = None
         Iterator = None
         Generator = None
+        Union = None
 
         class Enum:
             pass
@@ -70,4 +72,5 @@ __all__ = [
     "Callable",
     "Iterator",
     "Generator",
+    "Union",
 ]