Should we use namespacing in the CLI

@Microsoft/vscode https://github.com/microsoft/vscode/issues/92031 is requesting a terminal CLI to enable things like creating a new tab and splitting the current tab which would align with the capabilities of many terminals (including [Windows Terminal](https://github.com/microsoft/terminal/blob/master/doc/user-docs/UsingCommandlineArguments.md#using-the-wtexe-commandline)) and enable splitting a terminal tab by running a command in the terminal. Does anyone have opinions for or against this? If we want to go with this I think we should also do the same for extensions by deprecating/aliasing the current CLI and moving them to either `code ext ...` or `code extension ...` as it keeps growing and could be better organized: ``` Extensions Management --extensions-dir <dir> Set the root path for extensions. --list-extensions List the installed extensions. --show-versions Show versions of installed extensions, when using --list-extension. --category Filters installed extensions by provided category, when using --list-extension. --install-extension <extension-id | path-to-vsix> Installs or updates the extension. Use `--force` argument to avoid prompts. --uninstall-extension <extension-id> Uninstalls an extension. --enable-proposed-api <extension-id> Enables proposed API …