Share certificate bp2build between android_app and apex.

The certificate module is handled the same in Soong between android apps
and apexes, so share the bp2build code as well.

There are a few changes in this CL:

- If override_apex.certificate is unset, the generated apex also unsets
  it. This prevents the generated apex from using the base apex's
  certificate, which is most likely incorrect (e.g. google variant using
  the cert for the aosp variant). Instead, rely on the default
  certificate handling in the macro.
- If the certificate prop is a string, then it gets generated into
  certificate_name in order to disambiguate. This behavior is identical
  to android_app.

Test: added various unit tests.

Bug: 249089160
Fixes: 249089160
Change-Id: I99e18964ff546429a985d0f64dc21e2c69d35d9d

apex/apex.go

@@ -2659,9 +2659,13 @@ func (o *OverrideApex) ConvertWithBp2build(ctx android.TopDownMutatorContext) {
 		}
 
 		// Certificate
-		if overridableProperties.Certificate != nil {
-			attrs.Certificate = bazel.LabelAttribute{}
-			attrs.Certificate.SetValue(android.BazelLabelForModuleDepSingle(ctx, *overridableProperties.Certificate))
+		if overridableProperties.Certificate == nil {
+			// delegated to the rule attr default
+			attrs.Certificate = nil
+		} else {
+			certificateName, certificate := java.ParseCertificateToAttribute(ctx, overridableProperties.Certificate)
+			attrs.Certificate_name = certificateName
+			attrs.Certificate = certificate
 		}
 
 		// Prebuilts
@@ -3335,7 +3339,8 @@ type bazelApexBundleAttributes struct {
 	Android_manifest      bazel.LabelAttribute
 	File_contexts         bazel.LabelAttribute
 	Key                   bazel.LabelAttribute
-	Certificate           bazel.LabelAttribute
+	Certificate           *bazel.Label // used when the certificate prop is a module
+	Certificate_name      *string      // used when the certificate prop is a string
 	Min_sdk_version       *string
 	Updatable             bazel.BoolAttribute
 	Installable           bazel.BoolAttribute
@@ -3397,10 +3402,7 @@ func convertWithBp2build(a *apexBundle, ctx android.TopDownMutatorContext) (baze
 		keyLabelAttribute.SetValue(android.BazelLabelForModuleDepSingle(ctx, *a.overridableProperties.Key))
 	}
 
-	var certificateLabelAttribute bazel.LabelAttribute
-	if a.overridableProperties.Certificate != nil {
-		certificateLabelAttribute.SetValue(android.BazelLabelForModuleDepSingle(ctx, *a.overridableProperties.Certificate))
-	}
+	certificateName, certificate := java.ParseCertificateToAttribute(ctx, a.overridableProperties.Certificate)
 
 	nativeSharedLibs := &convertedNativeSharedLibs{
 		Native_shared_libs_32: bazel.LabelListAttribute{},
@@ -3456,7 +3458,8 @@ func convertWithBp2build(a *apexBundle, ctx android.TopDownMutatorContext) (baze
 		File_contexts:         fileContextsLabelAttribute,
 		Min_sdk_version:       minSdkVersion,
 		Key:                   keyLabelAttribute,
-		Certificate:           certificateLabelAttribute,
+		Certificate:           certificate,
+		Certificate_name:      certificateName,
 		Updatable:             updatableAttribute,
 		Installable:           installableAttribute,
 		Native_shared_libs_32: nativeSharedLibs.Native_shared_libs_32,