Handle long TabItems with complex, nested components more elegantly

[ptgott]

Sometimes, sets of instructions have multiple variations for two dimensions of use cases, but a Tabs component with a dropdown menu is inappropriate. For example, here is a situation in which we need to convey similar instructions for creating IAM policies for Teleport when the Database Service runs on Kubernetes and when the service runs on a Linux VM.

The "Linux Host" tab includes nested tab items:

The "Kubernetes Cluster" tab (partially shown here) includes code snippets but no nested tab items:

Another example is when a guide shows users how to install a Teleport agent on a Linux host and Kubernetes. The "Linux Host" tab needs to include a two-dimensional Tabs component, which creates clutter when placed within the TabItem:

Let's find a way to make long, complex TabItems more elegant. This will be especially important as we expand Kubernetes instructions to more pages within the documentation.