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)

App/CMakeLists.txt

@@ -24,6 +24,7 @@ if (DEFINED ENV{ESP_IDF_VERSION})
     )
 else()
 
+
     file(GLOB_RECURSE SOURCES "Source/*.c*")
     add_executable(AppSim ${SOURCES})
     target_link_libraries(AppSim
@@ -33,9 +34,11 @@ else()
         PRIVATE Simulator
     )
 
-    find_package(SDL2 REQUIRED CONFIG)
-    target_link_libraries(AppSim PRIVATE ${SDL2_LIBRARIES})
-    include_directories(${SDL2_INCLUDE_DIRS})
+    if (NOT DEFINED ENV{SKIP_SDL})
+        find_package(SDL2 REQUIRED CONFIG)
+        include_directories(${SDL2_INCLUDE_DIRS})
+        target_link_libraries(AppSim PRIVATE ${SDL2_LIBRARIES})
+    endif()
 
     add_definitions(-D_Nullable=)
     add_definitions(-D_Nonnull=)