RFR: 8155678: ClassLoader::initialize_module_loader_map should only be called when dumping CDS archive

[Jiangli Zhou]

Please review the following changes that make ClassLoader::initialize_module_loader_map() CDS dump time only. The module to loader map is not used by CDS runtime, so this avoids the unnecessary overhead for runtime. As part of the changes, I moved the ClassLoader::class loader_type() call from ClassLoader::load_class() into ClassLoaderExt::Context::record_result(), since ‘class loader_type’ is only needed by record_result(). That allows ClassLoader::class loader_type() become a CDS only API.

webrev: http://cr.openjdk.java.net/~jiangli/8155678/webrev.00/
bug: JDK-8155678 <https://bugs.openjdk.java.net/browse/JDK-8155678>

Thanks,
Jiangli