Fix incorrect relative/absolute URL usages (#29531)

Add two "HTMLURL" methods for PackageDescriptor. 
And rename "FullWebLink" to "VersionWebLink"

services/convert/package.go

@@ -35,7 +35,7 @@ func ToPackage(ctx context.Context, pd *packages.PackageDescriptor, doer *user_m
 		Name:       pd.Package.Name,
 		Version:    pd.Version.Version,
 		CreatedAt:  pd.Version.CreatedUnix.AsTime(),
-		HTMLURL:    pd.FullWebLink(),
+		HTMLURL:    pd.VersionHTMLURL(),
 	}, nil
 }