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)

sdkconfig.board.lilygo-tdeck

@@ -29,6 +29,7 @@ CONFIG_FATFS_LFN_HEAP=y
 CONFIG_FATFS_VOLUME_COUNT=3
 
 # Hardware: Main
+CONFIG_IDF_EXPERIMENTAL_FEATURES=y
 CONFIG_TT_BOARD_LILYGO_TDECK=y
 CONFIG_IDF_TARGET="esp32s3"
 CONFIG_ESP_DEFAULT_CPU_FREQ_MHZ_240=y
@@ -38,13 +39,15 @@ CONFIG_FLASHMODE_QIO=y
 # Hardware: SPI RAM
 CONFIG_ESP32S3_SPIRAM_SUPPORT=y
 CONFIG_SPIRAM_MODE_OCT=y
-CONFIG_SPIRAM_SPEED_80M=y
+CONFIG_SPIRAM_SPEED_120M=y
 CONFIG_SPIRAM_USE_MALLOC=y
 CONFIG_SPIRAM_TRY_ALLOCATE_WIFI_LWIP=y
+# SPI Flash (can set back to 80MHz after ESP-IDF bug is resolved)
+CONFIG_ESPTOOLPY_FLASHFREQ_120M=y
 # LVGL
 CONFIG_LV_DISP_DEF_REFR_PERIOD=17
 CONFIG_LV_INDEV_DEF_READ_PERIOD=17
 CONFIG_LV_DPI_DEF=139
 # USB
 CONFIG_TINYUSB_MSC_ENABLED=y
-CONFIG_TINYUSB_MSC_MOUNT_PATH="/sdcard"
+CONFIG_TINYUSB_MSC_MOUNT_PATH="/sdcard"