[Feature Request]: `TealAppDriver` gain a `get_tab_choices()` function

### Feature description

`TealAppDriver` has a method `navigate_teal_tab()` it would be nice to have `get_tab_choices()` function as well - then I could have a generic test which is "load app and navigate through all the tabs to make sure there are no validation errors".

Also, could `TealAppDriver` be exported? It's great functionality - I can use ::: of course in the meantime.

Would something like this work for me for now:

```r
get_tab_choices <- function(app_driver) {
html <- app_driver$get_html(".teal-modules-tree a")
paste(html, collapse = "") |>
rvest::read_html() |>
rvest::html_elements("a") |>
rvest::html_text() |>
trimws()
}
```

I'm not sure the best value to put in `get_html` to make sure I capture all modules and nothing else.

Thanks

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