Merge changes from topic "stub-impl-per-api-domain"

* changes:
  Special case platform variant of bootstrap libs
  Select stub/impl per apex variant
  For test apexes, base_apex_name is the api domain
  Broaden the granularity of config_setting from apex_name to api_domain
  Print default val if all vals in axis match default val

bazel/configurability.go

@@ -69,8 +69,8 @@ const (
 
 	productVariableBazelPackage = "//build/bazel/product_variables"
 
-	AndroidAndInApex  = "android-in_apex"
-	AndroidAndNonApex = "android-non_apex"
+	AndroidAndInApex = "android-in_apex"
+	AndroidPlatform  = "system"
 
 	InApex  = "in_apex"
 	NonApex = "non_apex"
@@ -202,7 +202,7 @@ var (
 
 	osAndInApexMap = map[string]string{
 		AndroidAndInApex:           "//build/bazel/rules/apex:android-in_apex",
-		AndroidAndNonApex:          "//build/bazel/rules/apex:android-non_apex",
+		AndroidPlatform:            "//build/bazel/rules/apex:system",
 		osDarwin:                   "//build/bazel/platforms/os:darwin",
 		osLinux:                    "//build/bazel/platforms/os:linux_glibc",
 		osLinuxMusl:                "//build/bazel/platforms/os:linux_musl",

bazel/properties.go

@@ -1434,4 +1434,6 @@ type StringMapAttribute map[string]string
 type ConfigSettingAttributes struct {
 	// Each key in Flag_values is a label to a custom string_setting
 	Flag_values StringMapAttribute
+	// Each element in Constraint_values is a label to a constraint_value
+	Constraint_values LabelListAttribute
 }