Add Manage Loadouts view and version-prefix-tolerant matching

[Coolgatty]

Description of the problem being solved:

Referenced Issues: #9451

Two related loadout pain points:

1. No way to manage a loadout as a whole. Deleting or reordering a loadout meant deleting/moving its passive tree, item set, skill set and config set one at a time across four separate Manage views. For example, moving a "Lvl 1" loadout to the top required individually moving each of its four sets.
2. Loadouts on a non-latest tree version stopped matching. A loadout whose passive tree is on an older/alternate version is shown with a [version] prefix (e.g. [3.28 (alternate)]). That prefix was compared against the plainly-named item/skill/config sets, so the loadout no longer grouped and dropped out of the loadouts dropdown.

This PR:

• Adds a Manage Loadouts... (ctrl-l) option to the loadouts dropdown that opens a management popup mirroring the Manage Passive Trees view. From it you can New / Rename / Copy / Delete and drag-reorder a loadout as a whole, so its tree, item, skill and config sets are created/renamed/copied/deleted/reordered together.
• Makes delete and rename skip a set that is the only one of its type or is shared by another loadout, so other loadouts stay intact.
• Folds the old New Loadout dropdown entry into the Manage view's New button.
• Fixes loadout name matching to use the plain set name (ignoring the [version] display prefix), so a loadout whose tree is on a non-latest version still groups with its plainly-named sets.

Steps taken to verify a working solution:

• Ran the app from source; opened the loadouts dropdown → Manage Loadouts... (and via Ctrl+L); created, renamed, copied, deleted and drag-reordered loadouts, and confirmed the tree / item / skill / config sets in each tab all changed together.
• Created a loadout, switched its tree to an alternate/older version, and confirmed it still appears and selects correctly from the loadouts dropdown.
• Added Busted tests (spec/System/TestManageLoadouts_spec.lua) covering version-prefix-tolerant matching, whole-loadout delete, and whole-loadout reorder.

Link to a build that showcases this PR:

N/A — reproducible on any build with multiple loadouts.

Before screenshot:

After screenshot:

[Coolgatty]

I noticed other attempts at implementing this in [ #9647 #9528 ] but they seem like attempts at a larger refactor of the loadout system.

My solution is a simpler implementation that looks to keep the same "feel", which can be improved upon if necessary.