Add support for Buck oncall annotations (#35562)

Summary:
Newer versions of Buck (not released open source) support an `oncall` annotation to denote who owns a particular BUCK file. These annotations are useful to support so that if BUCK files are updated with such annotations they don't break.

## Changelog

[Internal] [Changed] - support oncall annotation in BUCK files

Pull Request resolved: https://github.com/facebook/react-native/pull/35562

Test Plan: The `test_buck` CI job validates that the file can be evaluated by open-source Buck. I ran this on a CircleCI fork, and it passed.

Reviewed By: motiz88

Differential Revision: D41731925

Pulled By: cortinico

fbshipit-source-id: 7d0ae164c3e6289d4aa76892658d46bbe4faf99c

.buckconfig

@@ -15,3 +15,6 @@
 
 [alias]
   rntester = //packages/rn-tester/android/app:app
+
+[buildfile]
+  includes = //tools/build_defs/oss/preload.bzl

ReactAndroid/src/main/java/com/facebook/react/BUCK

@@ -1,5 +1,7 @@
 load("//tools/build_defs/oss:rn_defs.bzl", "react_native_dep", "react_native_target", "rn_android_library")
 
+oncall("react_native")
+
 rn_android_library(
     name = "react",
     srcs = glob(["*.java"]),

tools/build_defs/oss/preload.bzl

@@ -0,0 +1,4 @@
+# These are symbols that are available in newer versions of Buck, but not the open source one.
+
+def oncall(_team):
+    pass