remount: Detect when flashall has happened in the bootloader.

This adds a new metadata header flag to the super partition. This flag
is set when "adb remount" is used, and is implicitly cleared when
flashing.

If there is a scratch partition present on /data, we require that the
flag be set in order to proceed using overlays. If not set, scratch is
not mapped in first-stage init, and scratch images are removed later
during startup.

Bug: 297923468
Test: adb remount -R, touch file in out/, sync, flashall
Change-Id: I9cc411a1632101b5fc043193b38db8ffb9c20e7f
diff --git a/fastboot/task.h b/fastboot/task.h
index a98c874..7a713cf 100644
--- a/fastboot/task.h
+++ b/fastboot/task.h
@@ -52,7 +52,7 @@
               const bool apply_vbmeta, const FlashingPlan* fp);
     virtual FlashTask* AsFlashTask() override { return this; }
 
-    static bool IsDynamicParitition(const ImageSource* source, const FlashTask* task);
+    static bool IsDynamicPartition(const ImageSource* source, const FlashTask* task);
     void Run() override;
     std::string ToString() const override;
     std::string GetPartition() const { return pname_; }