CLI doesn't allow to forget all long running operation

[MBkkt]

At the moment ydb cli only supports

ydb operation list
ydb operation forget <id>
ydb operation cancel <id>

But each index creation/import/etc creates a long operation.
And some index creation operation can be quite large in SchemeShard LocalDB/in-memory state.
So sometimes user wants to delete all long operations that are already completed.