Missing menus in CommentSample

[rschnekenbu]

Some buttons generated by commands are missing in the comment sample since Theia release 1.28. This can be observed when the menu refactoring #11290 was applied. Before that refactoring, for example on theia 1.27, the buttons were displayed without issues and working.

This was discovered while working on PR #12007 and the issue #12231.
From what I could observe:

• Before refactoring, the buttons could be seen on the comment sample editor. The process to get the dialog is documented in this CommentThread state PR

• After refactoring, e.g. on Theia 1.28+, almost no buttons can be seen using same extension.

• The buttons are added back when the when and group entries are removed from the package.json of the extension (see https://github.com/microsoft/vscode-extension-samples/blob/4bef4529beb758da66d00f0ea708730267fd64fe/comment-sample/package.json#L104-L123). This may be an hint on the underlying issue. When the buttons are visible as the when and group entries are removed, the command can still not run. I could not trace what the main cause is for this failure.