Revert "Revert "aconfig: @hide generated Java code""

This reverts commit c0e8ffea41.

Reason for revert: The detected build breakage was unrelated to the aconfig change. Details in b/297881670#comment11.

Change-Id: Ia32bc2e796ed3de7fa049c2c2db340f4325a2853

tools/aconfig/src/codegen_java.rs

@@ -118,6 +118,7 @@ mod tests {
 
     const EXPECTED_FEATUREFLAGS_COMMON_CONTENT: &str = r#"
     package com.android.aconfig.test;
+    /** @hide */
     public interface FeatureFlags {
         @com.android.aconfig.annotations.AssumeFalseForR8
         boolean disabledRo();
@@ -132,6 +133,7 @@ mod tests {
 
     const EXPECTED_FLAG_COMMON_CONTENT: &str = r#"
     package com.android.aconfig.test;
+    /** @hide */
     public final class Flags {
         public static final String FLAG_DISABLED_RO = "com.android.aconfig.test.disabled_ro";
         public static final String FLAG_DISABLED_RW = "com.android.aconfig.test.disabled_rw";
@@ -163,6 +165,7 @@ mod tests {
     package com.android.aconfig.test;
     import java.util.HashMap;
     import java.util.Map;
+    /** @hide */
     public class FakeFeatureFlagsImpl implements FeatureFlags {
         public FakeFeatureFlagsImpl() {
             resetAll();
@@ -234,6 +237,7 @@ mod tests {
         let expect_featureflagsimpl_content = r#"
         package com.android.aconfig.test;
         import android.provider.DeviceConfig;
+        /** @hide */
         public final class FeatureFlagsImpl implements FeatureFlags {
             @Override
             public boolean disabledRo() {
@@ -316,6 +320,7 @@ mod tests {
         "#;
         let expect_featureflagsimpl_content = r#"
         package com.android.aconfig.test;
+        /** @hide */
         public final class FeatureFlagsImpl implements FeatureFlags {
             @Override
             public boolean disabledRo() {