[x] Change language code input to `ComboBoxInputWidget (filtering on input)`. Remove existing text input and button.
[x] To populate the combobox options, re-use data from one of the many choose language from list throughout wiki (most likely the current pop-up accessed by the `...` button)
[x] Combobox should preselect the default language
[x] Keep current behavior: nothing about language is passed to the wikitext unless the user selects something other than the default
[x] Section label remains `Language`
Nice to have:
[x] Format of dropdown options: Language name - Language code (ex. English - en)
 include local as an option in the dropdown - the label should be: `local (use language local to each map area)`
====Mock and specs
See epic: T318834
Goes into the attribute <mapframe lang="…"> (don’t forget the special case “local”)
We can reuse the existing list of languages in the "..." dialog.