SD card improvements (#214)

- Implement SD card locking logic and helper functions
- Fix issue with running ELF apps from SD card: this would crash when launched from the AppList
- Reduce Boot app wait time to 1 second
- Speed up boot by about 0.1 second by moving app&service registration to the Boot app
- Files app now uses proper SD card mount point name (and multiple SD cards)
- Removed `TT_SCREENSHOT_MODE`

TactilityHeadless/Source/hal/Hal.cpp

@@ -9,6 +9,8 @@
 
 #define TAG "hal"
 
+#define TT_SDCARD_MOUNT_POINT "/sdcard"
+
 namespace tt::hal {
 
 void init(const Configuration& configuration) {