[FL-2556] Update complete screen (#1332)

* Desktop: slideshow implementation
* Updater: handling splashscreen installation; added format version field to slideshow binary
* Desktop: added bidirectional slideshow navigation + instant cancel by "back" button; Updater: rebalanced update stages weights
* Updater: fixed missing field init; fixed potential loop when baking slideshows
* Assets: fixed "update complete" image to match original
* Desktop: added check for slideshow file version
* Scripts: slideshow.py cleanup
* Desktop: removed first start intro sequence
* Desktop: removed first start remnants

applications/updater/util/update_task.h

@@ -33,6 +33,7 @@ typedef enum {
 
     UpdateTaskStageLfsRestore,
     UpdateTaskStageResourcesUpdate,
+    UpdateTaskStageSplashscreenInstall,
 
     UpdateTaskStageCompleted,
     UpdateTaskStageError,
@@ -52,6 +53,7 @@ typedef enum {
     UpdateTaskStageGroupRadio = 1 << 4,
     UpdateTaskStageGroupPostUpdate = 1 << 5,
     UpdateTaskStageGroupResources = 1 << 6,
+    UpdateTaskStageGroupSplashscreen = 1 << 7,
 } UpdateTaskStageGroup;
 
 typedef struct {