Add core-platform-legacy to supported api surfaces

This is needed because `external/icu4j` creates two versions of the
`core-platform` API, one containing stable APIs and one containing
legacy APIs. It is not clear exactly what the difference is but as
they pass different `--show*-annotation` options to Metalava they need
to have their own `<api-surface>` element in the configuration.

Bug: 391554590
Test: m checkapi
Change-Id: Ie02abd17a289261fe47bfb9f2da0ca472f065d0d
diff --git a/java/java.go b/java/java.go
index d59c6ca..70ebebe 100644
--- a/java/java.go
+++ b/java/java.go
@@ -2318,6 +2318,7 @@
 	scopeOrderMap["core-platform"] = count + 2
 	scopeOrderMap["intra-core"] = count + 3
 	scopeOrderMap["core-platform-plus-public"] = count + 4
+	scopeOrderMap["core-platform-legacy"] = count + 5
 }
 
 func (al *ApiLibrary) sortApiFilesByApiScope(ctx android.ModuleContext, srcFilesInfo []JavaApiImportInfo) []JavaApiImportInfo {