RFR: 8241562: Rework nest host resolution/validation error support

[David Holmes]

webrev: http://cr.openjdk.java.net/~dholmes/8241562/webrev/

This is (hopefully) the last pre-integration cleanup for JEP-371: Hidden 
classes.

Rather than store the error message in a field of InstanceKlass we 
piggy-back onto the existing ResolutionErrorTable logic and add a new 
field to the ResolutionErrorEntry.

Also factored out the complex error message logic in linkResolver methods.

There's one code path in free_entry not covered by any existing testing 
so I will look at developing a test for that. Otherwise all new code 
paths have been tested.

Thanks,
David