Require native Git runtime and bundle full manpages

- Remove the app fallback path when native Git is unavailable and show a startup blocker instead
- Fix native level setup for staged file counting and cherry-pick parity
- Improve manpage loading/search and bundle full Git documentation assets
- Integrate Git cross-compilation into AndroidProjectTooling.sh and remove debug AAB support

app/src/main/assets/manpages/git-fsck-objects.txt

@@ -0,0 +1,22 @@
+git-fsck-objects(1)
+===================
+
+NAME
+----
+git-fsck-objects - Verifies the connectivity and validity of the objects in the database
+
+
+SYNOPSIS
+--------
+[verse]
+'git fsck-objects' ...
+
+DESCRIPTION
+-----------
+
+This is a synonym for linkgit:git-fsck[1].  Please refer to the
+documentation of that command.
+
+GIT
+---
+Part of the linkgit:git[1] suite