feat: support batch orchestration in non-currents

[DamienCassou]

The goal of this PR is to fix https://github.com/sorry-cypress/sorry-cypress/issues/766.

The corresponding change in sorry-cypress is at https://github.com/sorry-cypress/sorry-cypress/pull/859.

TODOs:

• [ ] add backward compatibility: when receiving 404 on /runs/:id/cy/instances (batch), never try again and instead use /runs/:id/instances (single instance).
• [ ] fix/add tests

[DamienCassou]

I'm closing this PR for now to clean up my todo list. Feel free to reopen when ready to do something about it.