Add a Menu Bar to Tesseratos

[RiscadoA]

Rebased on #1227.

Description

Adds a menu bar plugin to Tesseratos. This plugin basically picks up all entities with the MenuBarItem component, and shows them in the menu bar.

Additionally, ChildOf hierarchies lead to having drop-down menus within the bar.

Check out the editor main.cpp for an example of how these entities can be created. Down the road, we should change plugins to add their own entries there.

User interaction is handled through observers: if the user selects an item in the menu, the MenuBarSelected component is added and immediately removed. This triggers any .onAdd<MenuBarSelected> observers added by users.

Checklist

• [ ] Self-review changes.
• [x] Evaluate impact on the documentation.
• [x] Ensure test coverage.
• [x] Write new samples.
• [x] Add entry to the changelog's unreleased section.

[github-actions[bot]]

PR Preview Action v1.4.7 :---: :rocket: Deployed preview to https://GameDevTecnico.github.io/cubos/docs-preview/pr-1235/ on branch gh-pages at 2024-06-05 22:32 UTC

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 40.34%. Comparing base (50e078c) to head (73f8450).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1235 +/- ## ======================================= Coverage 40.34% 40.34% ======================================= Files 351 351 Lines 26050 26050 ======================================= + Hits 10509 10510 +1 + Misses 15541 15540 -1 ```

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