The upstream tview has gained support for a TextView widget, so the old
imported TextView is replaced. The big difference this brings is
ability to embed the TextView in a form, which significantly reduces the
complexity of the CommentForm page.

The github.com/rivo/uniseg module requires go 1.18 as a minimum version.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>