Review exception structure #794

For the v3 client, we use exception groups to group a sequence of retry exceptions, and also to group exceptions related to a bulk operation. In some cases, these groups can be nested, with retry groups inside of bulk operation exception groups.

We should review how we want to expose this, to make sure handling exceptions is user-friendly, and root causes are easy to determine.

Discussion here: #769 (comment)

We also have to make sure our exceptions follow the actionable error conventions, and that error details are properly exposed in error messages

ExceptionGroups should print some (or all) of the sub-exceptions for debugging, even on < 3.11