feat(accounts): Add batch operations for custom regions (#30922)

* feat(accounts): Add batch operations for custom regions

Added the following methods to the `RegionsService` in the Merchant API Accounts v1:
- `BatchCreateRegions`: Create multiple regions in a single request.
- `BatchUpdateRegions`: Update multiple regions in a single request.
- `BatchDeleteRegions`: Delete multiple regions in a single request.

These methods allow for more efficient management of custom regions.

PiperOrigin-RevId: 800519608

Source-Link: googleapis/googleapis@c4c5ad7

Source-Link: googleapis/googleapis-gen@d1fd7b2
Copy-Tag: eyJwIjoiZ29vZ2xlLXNob3BwaW5nLW1lcmNoYW50LWFjY291bnRzLXYxLy5Pd2xCb3QueWFtbCIsImgiOiJkMWZkN2IyZjAwZDVjNDI5ZTMxNzg5Yzk2YjU0ZTJjNWI4ZWI1M2JmIn0=

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

google-shopping-merchant-accounts-v1/.owlbot-manifest.json

@@ -313,6 +313,9 @@
     "snippets/programs_service/enable_program.rb",
     "snippets/programs_service/get_program.rb",
     "snippets/programs_service/list_programs.rb",
+    "snippets/regions_service/batch_create_regions.rb",
+    "snippets/regions_service/batch_delete_regions.rb",
+    "snippets/regions_service/batch_update_regions.rb",
     "snippets/regions_service/create_region.rb",
     "snippets/regions_service/delete_region.rb",
     "snippets/regions_service/get_region.rb",

google-shopping-merchant-accounts-v1/gapic_metadata.json

@@ -472,16 +472,31 @@
                 "create_region"
               ]
             },
+            "BatchCreateRegions": {
+              "methods": [
+                "batch_create_regions"
+              ]
+            },
             "UpdateRegion": {
               "methods": [
                 "update_region"
               ]
             },
+            "BatchUpdateRegions": {
+              "methods": [
+                "batch_update_regions"
+              ]
+            },
             "DeleteRegion": {
               "methods": [
                 "delete_region"
               ]
             },
+            "BatchDeleteRegions": {
+              "methods": [
+                "batch_delete_regions"
+              ]
+            },
             "ListRegions": {
               "methods": [
                 "list_regions"