Parameterize cc_stub_suite for api surface

cc_stub_suite now has an additional attribute correponding to the api
surface. This attribute will be used to pass additional args to the stub
generator.

Update bp2build to set the api_surface of the apex stubs. This ensures
that its stubs are generated with "--systemapi --apex"

Test: unit tests
Bug: 298085502
Change-Id: If4c479f85e6e485b5c795a565a0c559f1f013bf5
diff --git a/bp2build/testing.go b/bp2build/testing.go
index 0e7ef44..2924e9a 100644
--- a/bp2build/testing.go
+++ b/bp2build/testing.go
@@ -644,6 +644,7 @@
 		return ""
 	}
 	STUB_SUITE_ATTRS := map[string]string{
+		"api_surface":          "api_surface",
 		"stubs_symbol_file":    "symbol_file",
 		"stubs_versions":       "versions",
 		"soname":               "soname",