Feature: doc: Drop support for v1 cluster nodes with v3 remote nodes

As of this commit, Pacemaker Remote nodes or bundle nodes running
Pacemaker 3.0.0 or later are no longer supported with cluster nodes
running Pacemaker 1.y.z.

This also adds documentation for existing version compatibilities.

Closes T301

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>