Mark LaunchModeView as read-only

[50Wliu]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

Because it is. Should remove the need to special-case status-bar-launch-mode in the One themes.

Alternate Designs

None.

Benefits

Removal of special-casing in the One themes.

Possible Drawbacks

None.

Applicable Issues

None.

/cc @simurai is this worth doing?

[simurai]

@50Wliu is this worth doing?

Heh.... well, feel free to merge it. 🙇

On the other hand, we can also just keep it in the One themes for now. If it's a convention that all packages/themes should follow, we probably should make it part of the API. Currently it's a bit a wild-west where every package adds their own elements, functionality and styling. Having more consistency around it might be nice.