[6.14.z] hosts export selectable columns

[Satellite-QE]

Cherrypick of PR: https://github.com/SatelliteQE/robottelo/pull/14977

Problem Statement

The "Export" button in "All Hosts" page does not exports the visible columns as expected.

(https://bugzilla.redhat.com/show_bug.cgi?id=2167146)

Solution

New test for exporting only the selected columns in the web UI.

Related Issues

SAT-21626 (component evaluation)