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)

Documentation/ideas.md

@@ -12,8 +12,16 @@
 - M5Stack CoreS3 SD card mounts, but cannot be read. There is currently a notice about it [here](https://github.com/espressif/esp-bsp/blob/master/bsp/m5stack_core_s3/README.md).
 - EventFlag: Fix return value of set/get/wait (the errors are weirdly mixed in)
 - Consistently use either ESP_TARGET or ESP_PLATFORM
+- tt_check() failure during app argument bundle nullptr check seems to trigger SIGSEGV
+- Fix bug in T-Deck/etc: esp_lvgl_port settings has a large stack depth (~9kB) to fix an issue where the T-Deck would get a stackoverflow. This sometimes happens when WiFi is auto-enabled and you open the app while it is still connecting.
 
 # TODOs
+- Try to fix SDL pipeline issue with apt-get:
+  ```yaml
+  - name: Install SDL
+    run: sudo apt-get install -y libsdl2-dev cmake
+  ```
+- Make "blocking" argument the last one, and put it default to false (or remove it entirely?): void startApp(const std::string& id, bool blocking, std::shared_ptr<const Bundle> parameters) {
 - Boot hooks instead of a single boot method in config. Define different boot phases/levels in enum.
 - Add toggle to Display app for sysmon overlay: https://docs.lvgl.io/master/API/others/sysmon/index.html
 - CrashHandler: use "corrupted" flag