Default environment collector

This adds the default environment with type set to virtual and will always be applied.

Configuration

The environment plugin name is default.

=== ":octicons-file-code-16: pyproject.toml"

```toml
[tool.hatch.env.collectors.default]
```

=== ":octicons-file-code-16: hatch.toml"

```toml
[env.collectors.default]
```

There are no options available currently.