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-sh-i18n--envsubst.txt

@@ -0,0 +1,36 @@
+git-sh-i18n{litdd}envsubst(1)
+=============================
+
+NAME
+----
+git-sh-i18n--envsubst - Git's own envsubst(1) for i18n fallbacks
+
+SYNOPSIS
+--------
+[verse]
+eval_gettext () {
+	printf "%s" "$1" | (
+		export PATH $('git sh-i18n{litdd}envsubst' --variables "$1");
+		'git sh-i18n{litdd}envsubst' "$1"
+	)
+}
+
+DESCRIPTION
+-----------
+
+This is not a command the end user would want to run.  Ever.
+This documentation is meant for people who are studying the
+plumbing scripts and/or are writing new ones.
+
+'git sh-i18n{litdd}envsubst' is Git's stripped-down copy of the GNU
+`envsubst(1)` program that comes with the GNU gettext package. It's
+used internally by linkgit:git-sh-i18n[1] to interpolate the variables
+passed to the `eval_gettext` function.
+
+No promises are made about the interface, or that this
+program won't disappear without warning in the next version
+of Git. Don't use it.
+
+GIT
+---
+Part of the linkgit:git[1] suite