Add "Connect" buttons to Request Bridge and Provide Bridge modals

As part of #41617 (closed) for ~"Sponsor 30" we added a Connect button to the Built-in Bridges modal when Tor Browser is not connected. We planned on doing similar UX work to the Request Bridge and Provide Bridge modals too, but ran out of dev time on the project.

Instead we discussed copy-pasting the same button logic to the two other bridge modals instead so all three behave consistently – but it doesn't look like this happened.

If it's a relatively trivial fix, would it be possible to do this as a priority feature for the next alpha @richard? I think having consistent behavior between the three modals is important.