feat(devtools): add DevTool module for module management

[leandromqrs]

This pull request introduces a new "DevTool" developer utility panel for Aurora Shell, gated by the AURORA_DEVTOOLS environment variable. The DevTool provides a user interface for developers to interactively test and manage tray icons, replacing the previous hardcoded debug logic. It includes a new tray icon testing tool, associated UI styles, and a comprehensive integration test. The changes also clean up legacy debug code and ensure the DevTool is only available in development environments.

DevTool integration and tray icon testing:

• Added a new DevTool class (src/modules/devTool/devTool.ts) that provides a developer panel in the GNOME Shell status area when AURORA_DEVTOOLS=1 is set. This panel includes tabs for developer utilities, currently featuring tray icon testing tools.
• Implemented the TrayIconsDevTool class (src/modules/devTool/trayIconsDevTool.ts), allowing developers to add, remove, and trigger attention states on fake tray icons for testing purposes.
• Updated the extension's main entry (src/extension.ts) to enable or disable the DevTool based on the AURORA_DEVTOOLS environment variable, and to expose the DevTool instance for testing. [1] [2] [3] [4] [5] [6]

Testing and development environment:

• Added an integration test (tests/shell/auroraDevTool.js) to verify that the DevTool only appears when gated, and that tray icon actions work as expected.
• Modified the development shell script (scripts/run-gnome-shell.sh) to set AURORA_DEVTOOLS=1 for developer sessions, and removed legacy AURORA_TRAY_DEBUG logic. [1] [2]

UI and styling:

• Added new SCSS styles for the DevTool panel and its components (src/styles/_devtool.scss), and included them in both light and dark themes. [1] [2] [3]

Codebase cleanup:

• Removed old debug code that injected fake tray icons directly in the TrayIcons module, consolidating all such logic into the new DevTool.