tests: remove all remaining usage of experimental.bundle2-exp The only remaining usage of the experimental config were enforcing bundle2 on. These are very old remains of when bundle2 was off by default. This was also useful to highlight the fact that this was a bundle2 run and that a bundle1 one was nearby. However, we want a future developer working on bundle3 to notice possible output/behavior change on these tests and take them in account. So we do not enforce bundle2 for these runs. We leave a comment around to make sure dev still notice the bundle1 version.

tests: use 'legacy.exchange' option in various mixed tests The new option will stay around. The experimental option was only meant to be temporary. We update various tests that validate both bundle1 and bundle2 version side by side. This changeset only takes care of enforcing bundle1. The other use of 'experimental.bundle2-exp=True' will be taken care of in the next changeset.

tests: use 'legacy.exchange' option in various bundle1 tests The new option will stay around. The experimental option was only meant to be temporary.