bundle2: add a devel option controling bundle version used for exchange We need an official way to force bundle1 to be used in test. We introduce a new option 'devel.legacy.exchange' to control this. When specified, this option will control the list of bundle version Mercurial consider when exchanging with a peer. Current valid value are 'bundle1' and 'bundle2'. Using this option in all tests will allow us to remove the 'experimental.bundle2-exp' option. We will simplify the code once the experimental option is dropped.

bundle2: rename the _canusebundle2 method to _forcebundle1 We rename and invert the logic of the _canusebundle2 utility. The idea here is that we need to have a way to enforce the use of bundle1 in the tests. The Mercurial philosophy is to try to use the best method available. Currently that best method is bundle2, but this might change in the future. Therefore expressing "do not use bundle2" is a loosy way to say "use bundle 1" and will likely create issue in the future. As the config option will be explicitly about bundle1, we rename the function beforehand to align with this. This will make the life of a future developer working on bundle3 easier.

tests: remove bundle2 activation from test-bookmark-pushpull.t This is an old config that predate bundle2 on by default. This should have been remove after Mercurail 3.6 got released.