JDK 16 RFR of JDK-8248983: Add Name.isEmpty

[Joe Darcy]

Hello,

Please review the webev and CSR for

     JDK-8248983: Add Name.isEmpty
     CSR: https://bugs.openjdk.java.net/browse/JDK-8249005
     webrev: http://cr.openjdk.java.net/~darcy/8248983.0/

In its current form, this fix can only be pushed *after* the minimum 
boot JDK in the JDK 16 build is updated to JDK 15. Otherwise, the 
default method on CharSequence is not necessarily present.

To be pushed earlier, the default method on Name would need to be 
changed to host an implementation that didn't delegate to 
CharSequence.isEmpty. It would not be difficult to take that route 
instead with a follow-up bug to change the implementation of the default 
method later.

Thanks,

-Joe