Add option to disable the tab switcher popup while keeping tab switcher nextTab semantics

# Description of the new feature/enhancement

Having configured `"tabSwitcherMode": "mru"` I can not find an option to hide the (in my opinion distracting) tab switcher popup.

What I want is just MRU semantics on `nextTab` (especially when/if #9330 gets fixed) and no UI popup flashing by. If that can be achieved with `"tabSwitcherMode": "disabled"` that would be preferred.

# Proposed technical implementation details (optional)

Assuming the tab switcher is the only way to get MRU semantics when using `nextTab`, a new configuration key to control visibility of the tab switcher popup, e.g. `"showTabSwitcherInterface": true|false` (default: `true`).

Start by tracing how the "tabSwitcherMode" configuration and the "nextTab" command implement MRU behavior, then identify where the tab switcher popup is shown. Define whether "disabled" should preserve MRU semantics or whether a separate visibility option is needed, and verify that nextTab retains MRU behavior without displaying the popup.

Written by the indexing model from the issue text.