`multiple_text_inputs` example: Navigate to next input on submission (#24295)

# Objective

In the `multiple_text_inputs` example, the input focus should move to
the next text input after the user submits the input's contents.

## Solution

- In `submit_text`, after submission, use the `TabNavigation` system
param to find the next input, and set it as the `InputFocus`.
- Submit on just `Enter`. The `Ctrl` + `Enter` chord should be reserved
for inputs that allow new lines.