Fix index -1 exception in Manage Instances

[HebaruSan]

Problem

1. Open the manage game instances dialog
2. "Forget" all instances that have hours played (see Play Time #3543), if any; the Hours Played column will disappear if it was visible
3. Now add an instance that has hours played (again see Play Time #3543 for how to set this up), you'll get an exception and the instance list will fail to populate:

Noticed during dev of #3797 (in relation to the Game column instead), but I think I recall sporadic reports of this without those changes that I couldn't pin down at the time, so it seemed worth splitting into its own fix.

Cause

The list view has two columns that are sometimes visible and sometimes hidden: Game and Hours Played. To hide them, we remove them from the list view. If they become visible again, we insert them using their Column.Index property, which unfortunately is -1 for any column not already in the list:

• https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.columnheader.index?view=netframework-4.7

If the ColumnHeader is not contained within a ListView control this property returns a value of -1.

Inserting the column with an index of -1 throws an exception. This happens anytime a previously hidden column is supposed to become visible (including adding a KSP2 instance to a list of KSP1 instances in #3797).

Changes

Now instead of using the column's own index property, the show/hide helper function has an index parameter, into which we pass the index of the next column in the normal layout that is always visible. This makes the columns hide and reappear properly without exceptions.

[techman83]

Aha, yeah that makes sense. LGTM!