Support merging target files from directory

Expand `merge_target_files.py` API capabilities so that
`--framework-target-files` and `--vendor-target-files`
can be either zip archives or directories.

Test: Create a merged package by vendor target files folder
Test: atest --host releasetools_test
Bug: 276068400
Change-Id: I200be2a458ae59a61e05bfd7c78ab66093db32eb
diff --git a/tools/releasetools/merge/merge_meta.py b/tools/releasetools/merge/merge_meta.py
index 3288ef7..6fe3099 100644
--- a/tools/releasetools/merge/merge_meta.py
+++ b/tools/releasetools/merge/merge_meta.py
@@ -99,16 +99,16 @@
   """Merges various files in META/*."""
 
   framework_meta_dir = os.path.join(temp_dir, 'framework_meta', 'META')
-  merge_utils.ExtractItems(
-      input_zip=OPTIONS.framework_target_files,
+  merge_utils.CollectTargetFiles(
+      input_zipfile_or_dir=OPTIONS.framework_target_files,
       output_dir=os.path.dirname(framework_meta_dir),
-      extract_item_list=('META/*',))
+      item_list=('META/*',))
 
   vendor_meta_dir = os.path.join(temp_dir, 'vendor_meta', 'META')
-  merge_utils.ExtractItems(
-      input_zip=OPTIONS.vendor_target_files,
+  merge_utils.CollectTargetFiles(
+      input_zipfile_or_dir=OPTIONS.vendor_target_files,
       output_dir=os.path.dirname(vendor_meta_dir),
-      extract_item_list=('META/*',))
+      item_list=('META/*',))
 
   merged_meta_dir = os.path.join(merged_dir, 'META')