support metamodule, remove built-in overlayfs mount

Co-authored-by: weishu <twsxtd@gmail.com>
Co-authored-by: YuKongA <70465933+YuKongA@users.noreply.github.com>
Co-authored-by: Ylarod <me@ylarod.cn>

userspace/meta-overlayfs/metamodule/metainstall.sh

@@ -0,0 +1,61 @@
+#!/system/bin/sh
+############################################
+# meta-overlayfs metainstall.sh
+# Module installation hook for ext4 image support
+############################################
+
+# Constants
+IMG_FILE="/data/adb/metamodule/modules.img"
+MNT_DIR="/data/adb/metamodule/mnt"
+
+# Ensure ext4 image is mounted
+ensure_image_mounted() {
+    if ! mountpoint -q "$MNT_DIR" 2>/dev/null; then
+        ui_print "- Mounting modules image"
+        mkdir -p "$MNT_DIR"
+        mount -t ext4 -o loop,rw,noatime "$IMG_FILE" "$MNT_DIR" || {
+            abort "! Failed to mount modules image"
+        }
+        ui_print "- Image mounted successfully"
+    else
+        ui_print "- Image already mounted"
+    fi
+}
+
+# Post-installation: move partition directories to ext4 image
+post_install_to_image() {
+    ui_print "- Moving module content to image"
+
+    MOD_IMG_DIR="$MNT_DIR/$MODID"
+    mkdir -p "$MOD_IMG_DIR"
+
+    # Move all partition directories
+    for partition in system vendor product system_ext odm oem; do
+        if [ -d "$MODPATH/$partition" ]; then
+            ui_print "  Moving $partition/"
+            mv "$MODPATH/$partition" "$MOD_IMG_DIR/" || {
+                ui_print "! Warning: Failed to move $partition"
+            }
+        fi
+    done
+
+    # Set permissions
+    chown -R 0:0 "$MOD_IMG_DIR" 2>/dev/null
+    chmod -R 755 "$MOD_IMG_DIR" 2>/dev/null
+
+    ui_print "- Module content moved to image"
+}
+
+# Main installation flow
+ui_print "- Using meta-overlayfs metainstall"
+
+# 1. Ensure ext4 image is mounted
+ensure_image_mounted
+
+# 2. Call standard install_module function (defined in installer.sh)
+install_module
+
+# 3. Post-process: move content to image
+post_install_to_image
+
+ui_print "- Installation complete"