New `box.commit` and `box.atomic` option `wait`

Target: 3.2.0.

It can be passed like this: box.commit({wait = ...}) or
box.atomic({wait = ...}, ...). The possible values:

• 'complete' - default behaviour, block the current fiber until
  the txn is fully finished.
• 'submit' - send the txn to the journal, release the fiber.
  Completion happens asynchronously. Can block the fiber if the
  journal queue is full, until the txn can fit into the queue.
• 'none' - send the txn to the journal if the journal queue has
  space, otherwise fail right away. Commit with this option
  never yields.

In case of a Lua error being thrown the txn is rolled back, like
with the default behaviour, regardless of its wait mode.

The journal max size can be found and changed in
box.cfg.wal_queue_max_size. It affects when the wait modes
submit blocks and none fails.

TarantoolBot has missed the doc request somehow, so I've manually created the issue.
Source: https://github.com/tarantool/tarantool/pull/10225

The request concerns the box.commit({wait = ...}) and box.atomic({wait = ...}, ...) entry points; start by locating their existing API documentation. Document the complete, submit, and none modes, including wal_queue_max_size effects and rollback behavior, then verify the text matches the stated semantics.