Reapply "Add support for tests using androidx keep annotations"

This reverts commit 809cceb4534e1a1f1ca446a32bfa9fef13656cd2.

Reapply "Change the keep annotations in the androidx namespace to Kotlin source"

This reverts commit 8c2c3b1010ec081f0af519b8f8903d90229acde0.

With additional fix for SanityCheck.

Bug: b/392865072
Change-Id: I0d5dc671c4a7ea08960d92c28b5edf30e0e89627

src/keepanno/java/androidx/annotation/keep/MemberAccessFlags.kt

diff --git a/src/keepanno/java/androidx/annotation/keep/MemberAccessFlags.kt b/src/keepanno/java/androidx/annotation/keep/MemberAccessFlags.kt
new file mode 100644
index 0000000..4985630
--- /dev/null
+++ b/src/keepanno/java/androidx/annotation/keep/MemberAccessFlags.kt
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// ***********************************************************************************
+// MAINTAINED AND TESTED IN THE R8 REPO. PLEASE MAKE CHANGES THERE AND REPLICATE.
+// ***********************************************************************************
+
+package androidx.annotation.keep
+
+/**
+ * Valid matches on member access flags and their negations.
+ *
+ * <p>The negated elements make it easier to express the inverse as we cannot use a "not/negation"
+ * operation syntactically.
+ */
+enum class MemberAccessFlags {
+  PUBLIC,
+  NON_PUBLIC,
+  PROTECTED,
+  NON_PROTECTED,
+  PACKAGE_PRIVATE,
+  NON_PACKAGE_PRIVATE,
+  PRIVATE,
+  NON_PRIVATE,
+  STATIC,
+  NON_STATIC,
+  FINAL,
+  NON_FINAL,
+  SYNTHETIC,
+  NON_SYNTHETIC,
+}