Update react-router monorepo to v6

[bobsilverberg]

This is one of the remaining dependencies we have not yet updated due to changes needed. Getting to v6 is a multi-step process:

1. Update from v4 to v5. This should be a simple update.
2. Make some changes to our code with v5 to prepare for the update to v6.
3. Install the v5 to v6 compatibility package, which will allow some of our code can continue to use v5 while we migrate others, incrementally to v6.
4. Once all code has been migrated to work with v6, update to v6.

┆Issue is synchronized with this Jira Task

[bobsilverberg]

It looks like connected-react-router, which we are currently using, does not support react-router v6, so it doesn't make sense to try to update to react-router v6 at this point.

It is looking like connected-react-router is no longer in active development - there are a number of issues opened for it asking when support doe react-router v6 is coming, and none of them have responses from the maintainer.

An alternative that has been mentioned a number of times is redux-first-history, which I actually tried out back when I was upgrading other dependencies. I think that one works with react-router v6, so that might be the route to go. If so, we'll probably want to migrate first to redux-first-history from connected-react-router, and then update react-router to v6.