Introduce CacheImpl annotation

There is existing mechanism to provide different implementation for
instance to secure-store but one can replace only certain binding
with it (through provider class). In this case when H2CacheImpl is
installed it adds more bindings and replacing only this class would
keep leftovers being still initiated/running in Gerrit core.

CacheImpl annotation contains 2 types:
MEMORY
PERSISTENT
It is applied to modules that provide corresponding default caches
implementations.

When CacheImpl annotation is added to lib module then it will
override particular default implementation.

Change-Id: I7562b210fad4c5f6dc67887f627cf76815a378cb
Signed-off-by: Jacek Centkowski <jcentkowski@collab.net>

gerrit-war/src/main/java/com/google/gerrit/httpd/WebAppInitializer.java

@@ -34,6 +34,7 @@ import com.google.gerrit.pgm.util.LogFileCompressor;
 import com.google.gerrit.server.LibModuleLoader;
 import com.google.gerrit.server.StartupChecks;
 import com.google.gerrit.server.account.InternalAccountDirectory;
+import com.google.gerrit.server.cache.CacheOverrides;
 import com.google.gerrit.server.cache.h2.DefaultCacheFactory;
 import com.google.gerrit.server.change.ChangeCleanupRunner;
 import com.google.gerrit.server.config.AuthConfig;
@@ -364,8 +365,8 @@ public class WebAppInitializer extends GuiceServletContextListener implements Fi
         });
     modules.add(new GarbageCollectionModule());
     modules.add(new ChangeCleanupRunner.Module());
-    modules.addAll(LibModuleLoader.loadModules(cfgInjector));
-    return cfgInjector.createChildInjector(modules);
+    return cfgInjector.createChildInjector(
+        CacheOverrides.override(modules, LibModuleLoader.loadModules(cfgInjector)));
   }
 
   private Module createIndexModule() {