[Lacros] Implement GetMenuModel interface for Lacros web apps.

This CL:
1. Add crosapi interface to get the necessary menu items from
lacros-chrome
2. Create the menu model in the ash-chrome web app publisher

BUG=1144877

Change-Id: Iff4b198f6e60b2b2b84414483d53775e3bf03c34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2955259
Reviewed-by: Hidehiko Abe <[email protected]>
Reviewed-by: Dominick Ng <[email protected]>
Reviewed-by: Eric Willigers <[email protected]>
Commit-Queue: Maggie Cai <[email protected]>
Cr-Commit-Position: refs/heads/master@{#893268}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 16af9ee..3a4d656c 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -4807,6 +4807,7 @@
       "apps/app_service/app_web_contents_data.h",
       "apps/app_service/media_requests.cc",
       "apps/app_service/media_requests.h",
+      "apps/app_service/menu_item_constants.h",
     ]
   }