[vector-api] draft CSR for vector compress expand

[Paul Sandoz]

Hi,

See here:

  https://bugs.openjdk.java.net/browse/JDK-8277156

Now that https://github.com/openjdk/jdk/pull/5873 has been integrated I think we can merge vectorIntrinsics+compress into vectorIntrinsics, perhaps after master is merged into vectorIntrinsics?

Paul.