Don't show global column if not needed

# Don't show global column if not needed

## Context

Currently the global column is always shown, regardless of the number of severity configured for the project and the scenario tags.

## Expected

If there is only one severity and all scenarios of the project are tagged with this severity, then don't show the Global column in the executions.

(Same if none of the scenario are tagged with the unique severity, then show only the Global column and not the severity's one).

No files or tests are named. Start by locating the execution display code and searching for handling of the Global column, severity configuration, and scenario tags. Done means the column choices match both stated cases: hide Global when one severity covers all scenarios, and hide that severity column when no scenarios use it.

Written by the indexing model from the issue text.