www/node8: copy from www/node, update 8.8.1 -> 8.9.0 (LTS)

Create a new port for the latest Node.js 8.9.0 LTS release. Update
CONFLICTS for the existing Node.js ports to include the new node8 port
and remove non-existent ports.

https://nodejs.org/en/blog/release/v8.9.0/

Approved by: robak (mentor)
Differential Revision: https://reviews.freebsd.org/D12930