Change java codegen to read from new storage

This change adds code in java code to read from new storage. However the
generated code won't geneerate code contains code for new storage, since
the build system won't pass `allow-instrumentation` to java codegen.

Test: atest aconfig.test.java
Bug: 349874828
Change-Id: I70983fa97de6633f467d968109d134d46f895a89