Time & date, system events and much more (#152)

## Time & Date
- Added time to statusbar widget
- Added Time & Date Settings app
- Added TimeZone app for selecting TimeZone
- Added `tt::time` namespace with timezone code

## Other changes

- Added `SystemEvent` to publish/subscribe to system wide (e.g. for init code, but also for time settings changes)
- Changed the way the statusbar widget works: now there's only 1 that gets shown/hidden, instead of 1 instance per app instance.
- Moved `lowercase()` function to new namespace: `tt::string`
- Increased T-Deck flash & PSRAM SPI frequencies to 120 MHz (from 80 MHz)
- Temporary work-around (+ TODO item) for LVGL stack size (issue with WiFi app)
- Suppress T-Deck keystroke debugging to debug level (privacy issue)
- Improved SDL dependency wiring in various `CMakeLists.txt`
- `Loader` service had some variables renamed to the newer C++ style (from previous C style)

Boards/LilygoTdeck/Source/Lvgl.cpp

@@ -8,8 +8,8 @@
 
 // LVGL
 // The minimum task stack seems to be about 3500, but that crashes the wifi app in some scenarios
-// At 4000, it crashes when the fps renderer is available
-#define TDECK_LVGL_TASK_STACK_DEPTH 8192
+// At 8192, it sometimes crashes when wifi-auto enables and is busy connecting and then you open WifiManage
+#define TDECK_LVGL_TASK_STACK_DEPTH 9216
 
 bool tdeck_init_lvgl() {
     static lv_disp_t* display = nullptr;