Support pre-1.5 classes in CDS

Pre-1.5 classes are disabled during CDS dump time:

http://hg.openjdk.java.net/jdk/jdk/file/450d709262c1/src/hotspot/share/classfile/classFileParser.cpp#l5916

because in some cases, the pre-1.5 verification would need to execute Java code (to do some sort of rather mundane string encoding conversion ??). This used to a bad thing because we wanted to avoid executing Java code at dump time. However, now that we are using the Java class loaders anyway during dump time (since JDK 10), it seems no longer necessary to enforce this.

NOTE: we need to check if class constraint support can be support for these classes.