Lox bridge update can stop a bootstrap

Technically, if LoxTopics.UpdateBridges were to fire during a bootstrap it would end up cancelling the bootstrap because it changes the bridge settings.

This is in line with users changing their bridge settings also cancelling a bootstrap (#41921 (closed)). However, unlike those other cases, this would be unexpected from the user's point of view because they wouldn't have triggered it themselves.

I'm not 100% sure what the solution would be. We could delay the update until we are bootstrapped, or guarantee that the signal is not possible to generate prior to a bootstrap (#43305). However, it may be the case that we want to include some step within about:torconnect's flow to update lox bridges before being bootstrapped for cases where all bridges are blocked.

/cc @pierov