Define previous_api in full api surface stubs java_api_library defaults

previous_api input is required to migrate nullness information in
metalava and generate loosely equivalent from-text stubs. Since
"android.api.public.latest" is the only input for previous_api in the
tree, this is hardcoded for full api surface java_api_library modules
defaults for now.

Test: m && compare nullness annotations for from-text stubs and from-source stubs
Bug: 293962901
Change-Id: Ic07db8c3bd37fa41ff245952c94b5c5b4773af36
diff --git a/api/api.go b/api/api.go
index c568a45..a003aba 100644
--- a/api/api.go
+++ b/api/api.go
@@ -110,6 +110,7 @@
 	Api_surface         *string
 	Api_contributions   []string
 	Defaults_visibility []string
+	Previous_api        *string
 }
 
 type Bazel_module struct {
@@ -359,6 +360,7 @@
 		props.Api_contributions = transformArray(
 			modules, "", fmt.Sprintf(".stubs.source%s.api.contribution", apiSuffix))
 		props.Defaults_visibility = []string{"//visibility:public"}
+		props.Previous_api = proptools.StringPtr(":android.api.public.latest")
 		ctx.CreateModule(java.DefaultsFactory, &props)
 	}
 }