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`

Tactility/Source/app/ElfApp.cpp

@@ -6,6 +6,7 @@
 
 #include <Tactility/Log.h>
 #include <Tactility/StringUtils.h>
+#include <Tactility/hal/SdCard.h>
 
 #include "esp_elf.h"
 
@@ -49,7 +50,10 @@ private:
         assert(elfFileData == nullptr);
 
         size_t size = 0;
-        elfFileData = file::readBinary(filePath, size);
+        hal::withSdCardLock<void>(filePath, [this, &size](){
+            elfFileData = file::readBinary(filePath, size);
+        });
+
         if (elfFileData == nullptr) {
             return false;
         }