Refactor "staging dep on prod" allowlist dep

This allows branch-specific plugins to more easily add modules to
staging or prod mode allowlists (they need not separately ensure that
staging mode is a superset of prod mode)

Bug: 254447469
Test: TH
Test: Verified that adding tzdata modules via plugin (not part of
this CL) causes many outputs under bazel-out directories

Change-Id: I5d543e262a42cce324c59e3f9880b57ca209c13c

android/bazel_handler.go

@@ -389,9 +389,12 @@ func NewBazelContext(c *config) (BazelContext, error) {
 		}
 	case BazelStagingMode:
 		modulesDefaultToBazel = false
+		// Staging mode includes all prod modules plus all staging modules.
+		for _, enabledProdModule := range allowlists.ProdMixedBuildsEnabledList {
+			enabledModules[enabledProdModule] = true
+		}
 		for _, enabledStagingMode := range allowlists.StagingMixedBuildsEnabledList {
 			enabledModules[enabledStagingMode] = true
-
 		}
 	case BazelDevMode:
 		modulesDefaultToBazel = true