Remove the `Reachability.restrict` method--it hasn't been used since
2021, and was only kept around by mistake.
Remove the `Reachability.join` method--it was only used in the
circumstance where two flow control paths were being joined that had
equivalent reachability, in which case, it did nothing but return a
new reachability that was equivalent to one of its inputs. Call sites
have been updated to assert that the two control flow paths are indeed
equivalent, and then simply use the first control flow path's
reachability.
Change-Id: Ie24789ccd18723425b7db405d2122954dfae7b5b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/321841
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Paul Berry
5c018e5c65