Azure CLI with Bicep works differently

Hi, Team.

When I added the `azure-cli` feature to the devcontainer settings, I enabled the following option:

* `"installBicep": true`

Because it's a part of Azure CLI option, I was expecting that I would be able to use the following command:

```bash
az bicep version
```

However, it doesn't work. Rather it works in the following way:

```bash
bicep --version
```

It means that the Bicep CLI works as a standalone CLI instead of the part of Azure CLI. And I found the following codebase:

https://github.com/devcontainers/features/blob/7fa90110d762797cc0b1c2fe8fcc028c9b813d56/src/azure-cli/install.sh#L205-L208

Is there a reason that we use the standalone Bicep CLI, rather than Azure CLI integrated one?