Installing a dev container `feature` more than once in a `devcontainer.json`

The current [dev container features specification proposal](https://github.com/devcontainers/spec/blob/main/proposals/devcontainer-features.md#execution) is based on an array-like syntax for the 'features' attribute, and thus allows for the invocation of a single feature >1 with different options.

An execution goal stated in the spec is that
> "It should be possible to execute a feature multiple times with different parameters."

We are currently discussing how best to tackle [feature installation order (#43)](https://github.com/devcontainers/spec/issues/43), with the discussion leaning toward proceeding without use of an array, meaning that there is a need to explore other mechanisms for invoking a feature to install >1 times.

## Proposal

The propose extending the [value](https://github.com/devcontainers/cli/blob/main/src/spec-configuration/containerFeaturesConfiguration.ts#L33) to include an array of objects.

```jsonc
{
"image": "azcr.io/joshspicer/my-docker-image",
"features": {
"devcontainers/features/dotnet": [
{
"version": 3.1,
"runtimeOnly": true,
"installUsingApt": true
},
{
"version": 6.0,
"runtimeOnly": false,
"installUsingApt": false
}
]
}
}
```

This `devcontainer.json` will invoke the `devcontainers/features/dotnet` feature twice with two sets of options **in order** (first with the 3.1 set of arguments, and then 6.0 set of arguments).