[Nestmates] RFR: 8188076: [Nestmates] Rename MemberOfNest attribute to NestHost

[David Holmes]

webrev: http://cr.openjdk.java.net/~dholmes/8188076/webrev/

The MemberOfNest attribute was renamed to NestHost.

All references to nest-top now become nest-host.

There are some additional changes in 
test/langtools/tools/javac/valhalla/nestmate/CheckNestmateAttrs.java 
that were missed in previous commits.

Thanks,
David