feat(tabs): Enable rendering tabs list and tab content in independent locations

#### Feature Description

Currently, `MatTabGroup` renders the tab content immediately below the list of tab labels:
```
[ Tab 1 ] [ Tab 2 ] [ Tab 3 ]
-----------------------------
Tab content
```
This new feature will enable consumers to specify a separate location where the tab content should be rendered.

#### Use Case

The goal is to render content between the tab labels and tab content.

Example:
```
[ Tab 1 ] [ Tab 2 ] [ Tab 3 ] [ Button ]
---------------------------------------------------
Tab content
```

Usage example:
```

Content 1
Content 2
Content 3

Button

```

#### Contribution

I have an in progress PR that I will link to this issue.

Start with the MatTabGroup behavior described in the issue and review the provided usage example. Done means consumers can place tab content independently from the tab labels, with content rendered at the specified separate location.

Written by the indexing model from the issue text.