Design: allow changing historical API version filter in search?

[Eric-Arellano]

Follow up to https://github.com/Qiskit/documentation/issues/859.

We want to signal to the user that your search for the current API will be filtered to use the historical API version for that API, rather than the current version. For example, if you're at /api/qiskit/0.19, then we'll search Qiskit 0.19 rather than latest of 1.0. But we still use 'latest' for the other APIs like Runtime. So, show something like Qiskit SDK 0.19.

This shouldn't be a changeable element, meaning you don't change the search filter via the search bar. Instead, you change the API version with the API version switcher in the left sidebar:

One concern is how much screen real estate this label might take up, such as to show the text 'Qiskit IBM Runtime Client 0.17'.

Consider with the design how we'll want to handle translations, if we show when search is being filtered to e.g. Spanish.